Changes in vaccine administration trends across the life-course during the COVID-19 pandemic in the United States: a claims database study

ABSTRACT

Background

This study provides an updated and expanded analysis of the impact of the COVID-19 pandemic on routine vaccinations across the life-course in the United States.

Research design and methods

Routine wellness visits and vaccination rates were calculated using structured claims data for each month during the impact period (January 2020 to August 2022) and compared to the respective baseline period (January 2018 to December 2019). Monthly rates were aggregated as annual accumulated and cumulative percent changes.

Results

The complete monthly rate interactive dataset can be viewed at https://vaccinationtrends.com. The greatest decrease in annual accumulated administration rates in the 0–2 and 4–6 years age groups was for the measles, mumps, and rubella vaccine; for adolescents and older adults, it was for human papillomavirus and pneumococcal vaccines, respectively. Routine in-person wellness visit rates recovered faster and more completely than vaccination rates in all age groups, indicating potential missed opportunities to administer vaccines during visits.

Conclusions

This updated analysis reveals that the negative impact of the COVID-19 pandemic on routine vaccination continued through 2021 and into 2022. Proactive efforts to reverse this decline are needed to increase individual- and population-level vaccination coverage and avoid the associated preventable morbidity, mortality, and health care costs.

KEYWORDS:

• Vaccination
• immunization
• COVID-19
• adults
• pediatrics
• adolescents
• policy

1. Introduction

To reduce the transmission of COVID-19, stay-at-home orders and other public health measures were implemented in the United States (US) in early 2020 [1]. During this time the health care system experienced reduced capacity and the reallocation and reprioritization of resources, while patients and parents became concerned about exposure to COVID-19 in health care settings [2]. The combination of these and other factors has been associated with unintended consequences, including a reduced number of routine in-person wellness visits and vaccine administrations across all ages, most notably during early 2020 in the US, as well as globally [3–8]. Between 2019 and 2021, 67 million children worldwide missed out partially or entirely on receiving routine vaccinations, with the share of fully vaccinated children globally falling five percentage points to 81% [9]. Furthermore, there is evidence that vaccination hesitancy, including negative attitudes toward routine vaccination, may have increased during the pandemic, although the impact on vaccine uptake is still unclear [10–12].

Many vaccinations require high coverage rates to maintain community (‘herd’) immunity [13,14]. Prior to the COVID-19 pandemic, US coverage levels with some of the routine vaccinations recommended by the Advisory Committee on Immunization Practices (ACIP) were below national targets, most notably for human papillomavirus (HPV) vaccination among adolescents and for adult influenza and pneumococcal vaccinations [15–20]. During the US Department of Health and Human Services Healthy People 2020 health improvement initiative, the incidence of some vaccine-preventable diseases (including mumps and pertussis) increased compared to baseline, and there was little or no improvement in vaccination coverage with ≥4 doses of diphtheria, tetanus, and acellular pertussis (DTaP), Haemophilus influenzae type B (Hib), or pneumococcal vaccines among children 19–35 months of age; ≥2 doses of measles, mumps, and rubella (MMR) or ≥ 3 doses of polio vaccine among children in kindergarten; or pneumococcal vaccines among adults in long-term care [21]. Improving vaccination coverage among all age groups remains a major focus area of the updated Healthy People 2030 initiative [22].

Previous studies have found that vaccine administration rates decreased after the onset of the COVID-19 pandemic for ACIP-recommended routine childhood, adolescent, and adult vaccinations [4,6,7,23–31]. The magnitude of this decrease varied by age group and vaccine. Vaccination rates have improved since the initial decline in early 2020, but no studies to date have observed a complete recovery to pre-pandemic levels, nor the sustained higher rates of vaccination that are needed to make up for missed or delayed vaccinations [4,6,23–26,28,32,33].

In the US, the recent resurgence of measles and the community transmission of poliovirus strains highlight the public health risks associated with decreased vaccination coverage rates [34–36]. Vaccination coverage deficits have been projected to increase the clinical, health care system, and economic burdens of acute vaccine-preventable diseases and their long-term sequelae, such as HPV-related cancers, as well as cases of herpes zoster (shingles) caused by prior varicella infections [25,33,37–39]. It is thus important to understand, so as to eventually mitigate, any lingering impact of the COVID-19 pandemic on routine vaccination coverage across multiple age groups.

In a previous study, the impact of the COVID-19 pandemic on well-child visits and ACIP-recommended pediatric and adolescent vaccination rates from January 2018 to March 2021 was assessed [4]. The objective of the current study was to provide an updated and expanded analysis of the impact of the COVID-19 pandemic on in-person routine wellness visits across the life-course and the administration of ACIP-recommended pediatric, adolescent, and adult vaccines in the US. Further, we have included a longer post-2020 impact study period, adult age groups, and additional data analysis methodology, as well as provided access to an interactive dashboard to allow users to generate additional visualizations of the presented data.

2. Methods

2.1. Study design

This was a retrospective, cross-sectional analysis of structured claims data obtained from the Merative MarketScan Commercial Database with Early View, which allows for a preview of adjudicated claims data. The database contains de-identified medical and drug claims data for >215 million individuals covered by private health insurance in the US [40]. As the study database was formally certified as de-identified and all study procedures complied with the US Health Insurance Portability and Accountability Act, this study was exempt from Institutional Review Board approval and did not require informed consent [40].

The baseline (pre-COVID-19) period was defined as 1 January 2018 to 31 December 2019. The impact (COVID-19) period was defined as 1 January 2020 to 31 August 2022; the end date was selected based on our assessment that it was the last date for which the data were stable and unlikely to markedly fluctuate with further claims entry.

2.2. Study population

The study population comprised commercially insured individuals nationwide, of any age who resided in the US and were enrolled in the Merative™ MarketScan® MarketScan database with ≥1 medical claim recorded between 1 January 2018 and 31 August 2022. There were no continuous enrollment requirements, and the number of eligible enrollees was extracted for each month of the baseline and impact periods.

2.3. Variables

For all age groups, we recorded the number of relevant claims for each month during the baseline and impact periods. The vaccines of interest (Supplementary Tables S1, S2, & S3) and age groups were selected based on the 2018–2022 ACIP immunization schedules [41,42]. The age strata for the analyses were 0–2, 4–6, 9–16, 19–49, 50–64, and ≥65 years of age. To harmonize age groups with the published literature, data for individuals 17–18 years of age are included in the Supplementary Materials (Supplementary Tables S3 & S4, Supplementary Figures S1, S2, & S5).

The vaccinations evaluated for each age group are listed in Table 1. The rotavirus vaccine is not recommended for individuals >8 months of age and was therefore only counted for the subset of the 0–2 years group who were 0–1 year of age. Pneumococcal vaccination was included for individuals 19–64 years of age; however, in this age group immunization is only recommended for individuals with chronic medical conditions or other risk factors [43]. Influenza and COVID-19 vaccinations were excluded for all age groups and Hib, HPV, varicella, and MMR vaccinations were excluded for enrollees ≥18 years of age. We did not assess adult HPV vaccination because the ACIP expanded the recommendation in 2019 to include new age groups, with shared clinical decision-making now recommended for all adults aged 27–45 years, which would have impacted the baseline data [44]. Herpes zoster vaccines were also excluded due to atypical data distribution, likely due to supply shortages that drove aberrant administration patterns during the baseline and impact periods [45].

Table 1. Vaccine antigen or antigen group recorded for each age group.

Age group	0–2 years	4–6 years	9–16 years	19–49 years	50–64 and ≥65 years
Vaccines^A	DTaP Hepatitis A Hepatitis B Hib IPV MMR Pneumococcal Rotavirus^B Varicella	DTaP IPV MMR Varicella	HPV Meningococcal Tdap/Td	Hepatitis A Hepatitis B Meningococcal Pneumococcal Tdap/Td	Pneumococcal Tdap/Td

Note: DTaP, combined diphtheria, tetanus, and acellular pertussis vaccine; Hib, Haemophilus influenza type b; HPV, human papillomavirus; IPV, inactivated polio virus; MMR, combined measles, mumps, and rubella vaccine; Td, combined tetanus and diphtheria vaccine; Tdap, combined tetanus, diphtheria, and acellular pertussis vaccine.

^AIn-person wellness visits were also captured for each age group.

^BThe number of enrollees 0–1 years of age was used as the denominator for rotavirus vaccination rate calculations since the vaccine is not recommended after 8 months of age.

Counts were completed by antigen, or by antigen group in the case of MMR and tetanus-containing vaccines. For example, an individual receiving the DTaP-inactivated polio virus (IPV)-hepatitis B combination vaccine was included in each of the DTaP, IPV, and hepatitis B counts. In-person well-child and wellness visits and vaccinations were identified using the relevant Current Procedural Terminology and Healthcare Common Procedure Coding System codes (Supplementary Tables S1 & S2). Telemedicine wellness visits were excluded because only in-person visits offer opportunities for routine vaccine administrations, although telemedicine visits may play a role in vaccination referral.

2.4. Data analyses

We calculated 3 different measures of change for each age group and each vaccine antigen/antigen group (defined in detail below and represented mathematically in the Supplementary Text 1): i) the monthly percent change between the baseline period and the impact period, for every month from January 2020 to August 2022; ii) the annual accumulated percent change between the baseline period and each year of the impact period (2020, 2021, and January to August 2022); and iii) the cumulative percent change compared with baseline across time for every month of the impact period from January 2020 to August 2022.

The monthly rates of in-person wellness visits and vaccine administrations were calculated for each age group as the number of visits or vaccines administered each month divided by the number of individuals in that age group who were enrolled in the study database in that month. The monthly percent change was calculated as the percent difference between the rate for a given month in the impact period and the mean rate of the corresponding months in 2018 and 2019 (baseline period). We have developed an interactive dashboard that allows for further visualization of these data, which can be viewed at https://vaccinationtrends.com.

The additional measures, i.e., annual accumulated and cumulative percent changes, were derived from the expected number of in-person wellness visits or vaccine administrations during the impact period. For each age group, the expected number of wellness visits or vaccine administrations was calculated for each month of the impact period by multiplying the mean rate from the corresponding baseline months by the enrollment level in the month of interest. For example, to obtain the expected number of wellness visits or vaccine administrations in April 2020, we multiplied the baseline rate (the mean of the April 2018 and April 2019 rates) by the April 2020 enrollment level.

The annual accumulated percent change is the percent change between the expected and observed number of in-person wellness visits or vaccine administrations within a given year. Here, the expected number for a given year is the sum of the expected numbers for all months within that year. For 2022, this measure compares the expected and observed numbers from January through August (end of study period) rather than the entire year. This measure allows for a comparison of impact and baseline years without considering changes accumulated from the beginning of 2020, and it provides an estimate of the annual result of monthly variations.

The cumulative percent change for a given month is the total percent change between the expected and observed number of in-person wellness visits or vaccine administrations from January 2020 until the month of interest. For instance, the cumulative percent change in wellness visits for August 2021 compares the total number of expected and observed wellness visits between January 2020 and August 2021. This measure provides insight into how gains and losses accumulate over time relative to the baseline expectations.

3. Results

3.1. Study population

The mean number of enrollees in the study database each month during the baseline period/impact period was 4.6/3.9 million for enrollees 0–18 years of age, 10.9/9.4 million for enrollees 19–49 years of age, 5.7/4.9 million for enrollees 50–64 years of age, and 1.0/1.3 million for enrollees ≥65 years of age.

3.2. Wellness visits

The monthly rate of in-person wellness visits declined markedly relative to baseline for all age groups during the onset of the COVID-19 pandemic, i.e., from March to June 2020 (Tables 2–5). While some months with above-baseline monthly rates of wellness visits were observed later in 2020 and onward, these gains did not make up for the declines in prior months; the annual accumulated rate of wellness visits was below baseline in 2020 for all age groups, in 2021 for enrollees 0–2 and 4–6 years of age, and in 2022 for all age groups <50 years of age (Figure 1). When assessed annually, in 2020, children 0–2 years of age had the smallest decline in well-child visits (−3.4% compared to the expected rate), while in 2022, the smallest declines were observed for those 4–6 and 9–16 years of age (−5.3% and −5.5% compared to the expected rates, respectively). An analysis of the cumulative percent change demonstrated an incomplete recovery for wellness visits among all age groups in 2020, and for the entire study period among individuals 0–2, 4–6, and 19–49 years of age (Supplementary Figures S3-S8). For example, among individuals 9–16 years of age, although the monthly percent change in well-child visits peaked to 34.1% above baseline in September 2020 (Table 3), the cumulative percent change improved but remained negative throughout the study period, indicating an ongoing deficit (Figure 2).

Figure 1. Annual accumulated percent change in wellness visits and vaccine administration for 2020–2022 compared to 2018–2019 baseline period for enrollees (a) 0–2, (b) 4–6, (c) 9–16, (d) 19–49, (e) 50–64, and (f) ≥65 years of age.Note: DTaP, combined diphtheria, tetanus, and acellular pertussis vaccine; Hib, Haemophilus influenza type b; HPV, human papillomavirus; IPV, inactivated polio virus; MMR, combined measles, mumps, and rubella vaccine; Td, combined tetanus and diphtheria vaccine; Tdap, combined tetanus, diphtheria, and acellular pertussis.

Figure 1. (Continued).

Figure 2. Cumulative percent change in in-person well-child visits and human papillomavirus (HPV) vaccine administration among enrollees 9–16 years of age from January 2020 to August 2022, compared to equivalent data from the average of 2018 and 2019.

Table 2. Percent change in monthly well-child visits and vaccinations for enrollees 0–2 years of age from January 2020 to August 2022, compared to 2018–2019 baseline period.

	Well-child visits	DTaP	Hepatitis A	Hepatitis B	Hib	IPV	MMR	Pneumococcal	Rotavirus^A	Varicella
2020
January	2.7	2.7	9.5	3.5	2.8	2.7	6.1	2.9	2.7	6.4
February	0.4	0.6	3.3	1.9	0.8	1.8	−2.2	1.1	2.0	0.3
March	−14.3	−9.9	−19.0	−6.6	−9.9	−7.5	−17.3	−8.9	−5.4	−13.8
April	−20.7	−13.2	−28.5	−8.6	−12.6	−9.2	−28.0	−11.4	−5.3	−20.4
May	−6.3	−2.0	−1.2	−1.7	−1.9	−1.5	−14.3	−1.1	−1.7	−2.9
June	7.7	7.5	17.7	8.2	7.6	6.8	2.7	8.4	5.6	11.7
July	−1.3	0.9	3.1	0.4	0.4	1.6	−6.0	1.2	1.3	−0.2
August	−5.7	−4.8	−1.5	−4.5	−5.1	−4.3	−6.3	−4.1	−4.7	−3.0
September	3.7	5.7	8.0	5.2	5.7	6.2	1.9	5.3	5.1	5.2
October	−5.7	−4.9	−6.5	−5.0	−4.9	−5.1	−7.6	−5.0	−5.6	−4.6
November	−4.3	−4.0	−4.5	−2.9	−4.3	−3.5	−8.0	−4.1	−3.5	−2.9
December	5.4	7.4	9.6	7.2	7.4	7.5	1.9	7.0	6.1	6.4
2021
January	−8.4	−7.9	−3.2	−7.3	−7.9	−7.4	−6.5	−7.2	−7.4	−4.8
February	−2.4	−2.8	1.2	−1.2	−3.0	−1.8	−4.9	−2.7	−2.4	−0.6
March	8.4	6.5	14.8	7.8	6.0	6.9	8.4	6.6	6.1	13.1
April	−0.4	−2.3	2.1	0.1	−2.8	−2.1	−11.8	−2.4	−2.1	−3.0
May	−8.5	−9.9	−10.4	−8.4	−9.7	−8.5	−23.3	−9.2	−7.9	−12.4
June	7.9	5.6	5.6	6.5	6.2	6.7	−3.4	6.0	7.2	4.6
July	−3.0	−4.6	−4.5	−3.6	−4.7	−3.3	−10.6	−4.5	−2.9	−5.7
August	−2.1	−2.9	−6.5	−0.7	−3.2	−0.7	−7.2	−2.2	0.4	−5.8
September	4.9	5.9	2.8	8.4	6.2	7.9	−1.8	6.7	8.7	0.2
October	−7.6	−7.4	−11.7	−5.0	−7.6	−6.2	−13.7	−7.1	−5.8	−11.3
November	3.6	4.3	−2.1	8.3	3.9	6.0	−6.7	4.9	6.2	−3.2
December	2.9	3.7	−1.2	6.6	3.6	5.0	−9.2	3.0	3.9	−5.4
2022
January	−6.8	−4.3	−9.1	1.2	−4.3	−1.6	−14.3	−4.3	−1.0	−12.6
February	2.4	4.7	2.8	10.5	4.1	7.6	−1.3	5.6	6.4	1.3
March	2.1	6.2	7.1	10.3	5.8	8.3	4.5	7.1	6.9	7.2
April	−3.7	−3.5	−9.0	2.1	−3.4	−0.9	−15.2	−2.2	−1.0	−8.5
May	−3.4	−3.9	−6.2	1.0	−3.5	−1.7	−15.3	−2.4	−2.9	−4.7
June	4.3	5.9	1.7	10.8	6.6	7.7	−2.4	7.1	6.2	5.3
July	−10.0	−9.5	−13.4	−5.5	−9.4	−7.9	−13.6	−8.6	−9.7	−9.3
August	0.5	0.7	0.9	6.5	0.3	2.5	1.6	1.4	−0.2	2.6

Note: DTaP, diphtheria, tetanus, and acellular pertussis vaccine; Hib, Haemophilus influenza type b; IPV, inactivated polio virus; MMR, measles, mumps, and rubella; Td, combined tetanus and diphtheria vaccine; Tdap, combined tetanus, diphtheria, and acellular pertussis vaccine. Percent differences were calculated as the percent change in the rate for each month relative to the average monthly rate from the baseline period (1 January 2018 to 31 December 2019). Interactive visualizations of these monthly data can be viewed at https://vaccinationtrends.com.

^AThe number of enrollees 0–1 years of age was used as the denominator for rotavirus vaccination rate calculations since the vaccine is not recommended after 8 months of age.

Table 3. Percent change in monthly well-child visits and vaccinations for enrollees 4–6 and 9–16 years of age from January 2020 to August 2022, compared to 2018–2019 baseline period.

Age group	4–6 years					9–16 years
Vaccine	Well-child visits	DTaP	IPV	MMR	Varicella	Well-child visits	HPV	Meningococcal	Tdap/Td
2020
January	5.6	4.9	4.7	3.2	4.7	10.4	7.2	7.4	4.3
February	4.5	−1.1	−1.1	−4.5	−1.4	7.6	2.8	3.8	2.1
March	−34.9	−36.4	−36.2	−37.6	−36.2	−32.7	−34.1	−35.1	−37.8
April	−65.8	−64.6	−64.4	−66.3	−65.0	−71.2	−72.1	−72.9	−72.7
May	−27.4	−24.5	−24.2	−29.6	−26.3	−40.1	−37.7	−39.6	−40.0
June	20.0	21.2	21.0	14.9	18.8	−2.6	−3.4	−2.8	−6.0
July	7.4	3.7	3.8	−0.6	1.6	−4.8	−8.0	−8.1	−12.6
August	−6.9	−10.1	−10.0	−13.5	−12.5	−12.4	−14.5	−13.8	−15.8
September	23.4	22.6	22.4	17.7	19.1	34.1	28.6	36.7	37.3
October	10.4	8.6	8.7	5.8	7.3	17.9	5.7	21.9	25.3
November	0.8	0.9	0.4	−1.9	−0.9	7.7	−3.0	9.4	9.7
December	4.5	4.1	4.3	1.6	3.2	14.3	2.3	15.5	14.2
2021
January	−9.7	−6.8	−6.1	−9.4	−7.0	−2.5	−8.0	0.7	1.3
February	−1.4	−1.1	−0.5	−4.3	−1.3	6.3	−2.2	10.8	9.9
March	8.6	7.9	8.0	5.0	7.1	24.8	21.5	29.4	26.7
April	−17.3	−15.3	−15.0	−19.3	−16.7	−4.1	0.2	−3.4	−1.3
May	−16.5	−18.9	−19.0	−23.8	−21.1	−13.0	−20.9	−17.1	−14.8
June	11.2	6.0	5.8	1.9	4.9	2.0	−14.4	−3.2	−5.5
July	−0.2	−3.5	−3.7	−5.1	−4.4	−4.7	−13.9	−5.2	−10.8
August	−8.6	−11.1	−11.1	−12.0	−11.5	−9.8	−17.8	−11.7	−14.6
September	5.6	1.2	1.3	−0.7	0.2	11.3	−1.8	3.9	0.1
October	−7.3	−10.7	−11.0	−12.0	−11.0	−2.7	−18.3	−5.5	−5.9
November	5.8	0.3	0.0	−2.0	−1.6	11.4	−9.5	2.4	0.8
December	8.0	0.2	0.2	−0.9	−0.3	14.3	−10.4	6.5	6.8
2022
January	−14.3	−15.3	−15.0	−17.5	−15.8	−7.9	−25.0	−12.8	−12.5
February	0.7	−3.9	−3.7	−6.3	−4.3	7.7	−11.7	4.1	3.6
March	9.3	2.6	2.6	0.6	3.1	18.0	−1.0	14.9	10.8
April	−7.8	−14.5	−14.4	−18.6	−16.2	2.9	−13.9	−7.1	−10.6
May	−9.1	−16.0	−15.9	−20.3	−17.8	−7.6	−21.1	−17.4	−19.7
June	4.0	−0.2	−0.5	−3.0	−1.3	−3.0	−15.3	−6.3	−9.4
July	−12.9	−14.7	−15.1	−16.6	−16.0	−17.3	−27.8	−17.0	−21.6
August	−8.0	−8.6	−8.0	−9.6	−9.6	−11.1	−20.6	−11.9	−16.0

Note: DTaP, diphtheria, tetanus, and acellular pertussis vaccine; HPV, human papillomavirus; IPV, inactivated polio virus; MMR, measles, mumps, and rubella; Td, combined tetanus and diphtheria vaccine; Tdap, combined tetanus, diphtheria, and acellular pertussis vaccine. Percent differences were calculated as the percent change in the rate for each month relative to the average monthly rate from the baseline period (1 January 2018 to 31 December 2019). Interactive visualizations of these monthly data can be viewed at https://vaccinationtrends.com.

Table 4. Percent change in monthly in-person wellness visits and vaccinations for enrollees 19–49 years of age from January 2020 to August 2022, compared to 2018–2019 baseline period.

Vaccine	Wellness visits	Hepatitis A	Hepatitis B	Meningococcal	Pneumococcal	Tdap/Td
2020
January	6.0	−4.2	3.7	−13.1	16.3	10.4
February	6.2	−7.8	4.8	−14.7	17.8	9.2
March	−31.0	−52.6	−34.1	−44.9	7.6	−19.0
April	−75.5	−88.7	−69.2	−73.3	−72.6	−49.4
May	−53.5	−82.0	−58.0	−56.8	−56.2	−39.0
June	−7.0	−64.8	−32.6	−40.0	−14.6	−13.3
July	1.1	−56.9	−22.7	−24.3	−3.7	−9.2
August	−8.1	−58.0	−27.8	−33.4	−6.1	−14.2
September	9.9	−57.4	−22.4	−31.5	13.3	−1.7
October	1.7	−65.2	−33.6	−29.7	0.0	−10.3
November	−0.5	−72.7	−34.4	−40.3	−10.9	−11.0
December	5.5	−70.6	−26.0	−35.9	−7.9	−3.7
2021
January	−7.9	−73.0	−36.7	−36.6	−22.5	−14.4
February	−2.6	−73.5	−37.0	−39.4	−25.5	−10.4
March	11.3	−71.4	−37.3	−32.3	−32.3	−7.1
April	−3.4	−81.0	−46.0	−42.9	−48.9	−23.2
May	−13.1	−79.2	−41.5	−48.8	−35.4	−19.5
June	7.3	−67.4	−23.2	−33.6	−8.0	3.9
July	0.3	−68.2	−26.0	−30.6	−12.8	−3.5
August	−2.4	−69.5	−28.5	−31.9	−18.6	−6.6
September	7.9	−70.4	−30.7	−36.6	−24.8	−3.0
October	−6.0	−75.3	−42.0	−44.4	−38.8	−17.9
November	6.0	−76.3	−35.6	−40.5	−33.5	−9.9
December	4.4	−75.3	−34.1	−45.7	−32.4	−9.1
2022
January	−10.5	−74.8	−41.9	−51.4	−35.5	−14.9
February	1.7	−71.3	−35.3	−45.4	−22.4	−5.3
March	10.7	−68.2	−32.2	−42.1	−13.7	1.8
April	0.0	−72.3	−35.2	−36.6	−14.4	−7.2
May	−4.7	−76.5	−38.6	−43.0	−8.5	−12.0
June	4.4	−69.9	−25.8	−39.6	18.4	−3.9
July	−10.3	−72.8	−29.6	−44.8	3.2	−16.6
August	−1.0	−70.2	−19.4	−40.5	19.3	−8.3

Note: HPV, human papillomavirus; Td, combined tetanus and diphtheria vaccine; Tdap, combined tetanus, diphtheria, and acellular pertussis vaccine. Percent differences were calculated as the percent change in the rate for each month relative to the average monthly rate from the baseline period (1 January 2018 to 31 December 2019). Interactive visualizations of these monthly data can be viewed at https://vaccinationtrends.com.

Table 5. Percent change in monthly in-person wellness visits and vaccinations for enrollees 50–64 and ≥65 years of age from January 2020 to August 2022, compared to 2018–2019 baseline period.

Age group	50–64 years			≥65 years
Vaccine	Wellness visits	Pneumococcal	Tdap/Td	Wellness visits	Pneumococcal	Tdap/Td
2020
January	8.6	0.1	13.5	3.0	−9.2	−5.9
February	8.9	−0.4	9.1	0.6	−12.9	−6.7
March	−29.0	8.9	−28.4	−37.6	−32.7	−37.2
April	−73.3	−70.8	−69.2	−75.2	−84.0	−68.2
May	−48.0	−51.1	−49.3	−46.6	−62.8	−47.5
June	1.1	−8.3	−15.2	14.8	−10.4	−12.6
July	6.5	0.1	−10.7	20.0	5.3	−11.5
August	−1.0	4.6	−11.4	12.5	6.1	−9.6
September	15.4	24.4	−2.1	25.5	14.1	−4.9
October	3.3	−3.1	−11.3	2.0	−18.2	−17.0
November	0.2	−8.9	−10.8	1.3	−23.0	−19.3
December	4.5	−7.1	−9.3	6.8	−22.5	−21.2
2021
January	−6.6	−32.8	−20.5	5.3	−44.7	−43.3
February	−1.6	−41.0	−21.3	11.0	−65.7	−50.4
March	13.1	−51.3	−28.0	28.0	−63.6	−41.2
April	−8.1	−60.5	−42.0	2.9	−48.8	−32.5
May	−14.5	−45.1	−25.3	−3.5	−43.1	−28.0
June	10.3	−24.0	−1.5	36.2	−18.5	−12.8
July	4.0	−22.7	−8.1	27.6	−16.4	−16.5
August	3.4	−25.8	−11.5	31.5	−15.8	−18.9
September	12.8	−34.0	−9.6	39.0	−30.2	−21.3
October	−3.0	−52.5	−24.0	12.7	−54.3	−34.3
November	8.9	−46.4	−16.3	27.9	−46.8	−24.8
December	6.8	−40.0	−14.0	25.4	−40.2	−27.7
2022
January	−5.9	−46.2	−20.0	6.7	−47.6	−30.7
February	5.3	−35.7	−4.5	20.5	−40.1	−18.6
March	14.7	−23.8	5.2	33.5	−29.4	−6.3
April	1.0	−21.9	−5.8	19.6	−27.6	−13.5
May	−3.8	−9.8	−13.0	16.5	−27.3	−16.6
June	6.7	16.4	−4.9	40.4	−12.9	−10.1
July	−7.4	10.4	−17.0	21.9	−21.0	−18.8
August	4.1	24.3	−8.3	42.0	−9.5	−9.6

Note: Td, combined tetanus and diphtheria vaccine; Tdap, combined tetanus, diphtheria, and acellular pertussis vaccine. Percent differences were calculated as the percent change in the rate for each month relative to the average monthly rate from the baseline period (1 January 2018 to 31 December 2019). Interactive visualizations of these monthly data can be viewed at https://vaccinationtrends.com.

3.3. Pediatric vaccinations

3.3.1. Vaccine administration rates for individuals 0–2 years of age

The monthly rate of administration of all vaccines recorded for enrollees 0–2 years of age fell sharply in April 2020 compared to pre-pandemic rates, with the percent decrease ranging from −8.6% for hepatitis B to −28.0% for MMR and −28.5% for hepatitis A (Table 2, Supplementary Figure S1A). Although monthly administration rates subsequently increased, the annual accumulated vaccine administration rate remained below the average 2018–2019 baseline level for many of the vaccines recorded for this age group throughout the entire study period (Figure 1a). The greatest overall decreases were observed for MMR vaccine administrations, which had an annual accumulated percent change compared to baseline of −6.8%, −7.9%, and −7.3%, in 2020, 2021, and 2022, respectively. In contrast, the annual accumulated administration rate recovered to levels at or above the baseline for some vaccines in this age group, with the greatest increase being observed for hepatitis B vaccines (annual accumulated changes of 0.7% and 4.5% above baseline levels in 2021 and 2022, respectively; Figure 1a).

During the baseline period, the annual accumulated MMR vaccine administration rate increased by 11.6% in 2019 compared to 2018, likely due to an increased number of domestic measles cases and outbreaks [46]. We therefore performed additional annual accumulated administration rate analyses for this vaccine using 3 baseline periods: 2018 alone, 2019 alone, and the mean for 2018–2019 (Supplementary Figure S9). When compared to baseline data from 2018 alone, the annual accumulated percent change in MMR vaccine administration was −1.6%, −2.8%, and −0.2% for 2020, 2021, and 2022, respectively, representing a smaller decrease than when data from the impact period were compared to the mean of 2018 and 2019.

For all vaccines recorded for individuals 0–2 years of age, the cumulative percent change in administration rate compared to the 2018–2019 average improved after the initial sharp drop but remained negative throughout 2020 for all vaccines (Supplementary Figure S3). The cumulative percent change in MMR vaccine administration remained below all 3 baseline levels throughout the impact period; the decrease was greatest compared to the baseline data from 2019 alone and smallest compared to the baseline data from 2018 alone.

3.3.2. Vaccination rates for individuals 4–6 years of age

All vaccines recorded for enrollees 4–6 years of age experienced a similar decline in administration rates in April 2020 compared with pre-pandemic rates, ranging from −64.4% for the IPV vaccine to −66.3% for MMR (Table 3, Supplementary Figure S4). The annual accumulated administration rate for all vaccines recorded for this age group partially improved in 2021 compared to 2020, albeit to levels that were still lower than baseline (Figure 1b). In 2022, with data available from 1 January to 31 August, the annual accumulated vaccine administration rate decreased further, to below 2020 levels: −9.1% compared to baseline for DTaP, −9.0% for IPV, −10.1% for varicella, and −11.6% for MMR.

As with the 0–2 years age group, above, we performed additional analyses for MMR to account for the increase in vaccination rates in 2019 compared to 2018. The annual accumulated MMR vaccine administration rate among this age group was negative for all 3 baseline comparisons. The declines compared to the 2018 baseline were smaller than were the declines compared to the average 2018–2019 baseline, at −8.5% in 2020, −5.6% in 2021, and −9.2% in 2022 (Supplementary Figure S9). For all vaccines in this age group, the cumulative percent change in administration rate remained negative throughout the study period (Supplementary Figure S4).

3.3.3. Vaccination rates for individuals 9–16 years of age

The monthly administration rates of all 3 vaccines recorded for enrollees 9–16 years of age (HPV, meningococcal, and Tdap) declined in April 2020 by 72–73% (Table 3, Supplementary Figure S5). In 2021, meningococcal and tetanus-containing vaccines experienced a partial improvement in annual accumulated administration rates compared to 2020 but remained below baseline levels; the rate of administration fell to below 2020 levels in 2022 (data from 1 January to 31 August) in both cases. The 2021 recovery in the annual accumulated vaccine administration rate was weaker for HPV (−10.0%) than for Tdap (−4.4%) and meningococcal (−2.6%) vaccines; the HPV rate decreased further in 2022, to −18.6% below baseline (Figure 1c). The cumulative percent change in the administration rate of HPV vaccines remained negative during the entire study period, with some evidence of a growing deficit over time (Figure 2, Supplementary Figure S5). Although the rates of HPV vaccination and well-child visits among this age group experienced similar initial declines, the cumulative percent change recovery was weaker for HPV vaccination (Figure 2).

3.4. Adult vaccinations

3.4.1. Vaccination Rates for individuals 19–49 years of age

Among the vaccines recorded for enrollees 19–49 years of age, the greatest decline in monthly administration rates in April 2020 was observed for the hepatitis A vaccine (−88.7%) and the smallest for the Tdap/Td vaccine (−49.4%; Table 4, Supplementary Figure S1E). Among this age group, the 2021 annual accumulated percent changes in hepatitis A, hepatitis B, meningococcal, and pneumococcal vaccine administration rates exhibited a weaker recovery than was seen in 2020; this recovery was also weaker than that of most pediatric and adolescent vaccinations (Figure 1d). The 2022 annual accumulated administration rates remained lower than baseline levels for all vaccines recorded for this age group, with a range from −7.2% for pneumococcal vaccines to −72.2% for hepatitis A vaccines. The cumulative percent change in administration rate remained negative for the entire study period for all 5 vaccines recorded for this age group (Supplementary Figure S6).

3.4.2. Vaccination Rates for individuals ≥50 years of age

The overall monthly patterns of Tdap/Td and pneumococcal vaccine administrations were broadly similar between the 50–64 and the ≥65 years age groups (Table 5, Supplementary Figure S1E-F). The annual accumulated administration rate was lowest in 2021 for both vaccines in both age groups and had only partially improved by August 2022, when the annual accumulated percent change compared to baseline was −8.7% for Tdap/Td vaccines and −12.6% for pneumococcal vaccines among enrollees 50–64 years of age, and −15.5% for Tdap/Td vaccines and −28.3% for pneumococcal vaccines among those ≥65 years of age (Figure 1e-f). Despite these partial recoveries, the cumulative percent change in administration rate of both vaccines remained negative during the entire study period in both age groups (Supplementary Figures S7 and S8).

4. Discussion

In this study, we expanded a previous analysis [4] of the impact of the COVID-19 pandemic on routine vaccination uptake by including adult vaccination, lengthening the timeline of the analysis through August 2022, and including additional analysis methods. The 2020 annual accumulated rates of in-person wellness visits and recommended vaccinations were below baseline levels for all age groups to varying degrees. In 2021, the annual accumulated rate of wellness visits recovered to some extent in all age groups and exceeded the baseline level for individuals 9–16, 50–64, and ≥65 years of age, although the cumulative percent change remained negative throughout the entire study period for all but the latter group. Weaker recoveries were observed for almost all routine vaccine administrations recorded for each age group, and many vaccination deficits persisted through the end of the study period, i.e., until August 2022. Particularly large deficits were observed for HPV vaccination among adolescents 9–16 years of age, hepatitis A vaccination among those 19–49 years of age, and pneumococcal vaccination among adults ≥65 years of age.

The current study is in line with earlier reports that declines in in-person wellness visits and routine vaccine administrations occurred in the US during the early stages of the pandemic among all age groups, but improved to some extent later in 2020 [4,6,7,23–31]. Similar trends have been reported for other countries, demonstrating the persistent and widespread impact of the COVID-19 pandemic on individual- and community-level immunity and on global public health [8,47–50]. The longer study period and additional age groups used for the current study allowed us to build on a previous analysis [4] and to observe that routine vaccine administration deficits generally continued throughout 2021 for all pediatric, adolescent, and adult age groups, and in many cases persisted though the August 2022 study impact period.

Across the different age groups, the annual accumulated rates of in-person wellness visits and vaccine administrations declined the least among the 0–2 years age group, except for MMR vaccination. Indeed, during the pandemic, the American Academy of Pediatrics has urged routine well-child visits and vaccinations to continue, especially among children ≤2 years of age [51]. The rate of hepatitis B vaccination among this age group increased in 2022, likely due to the introduction of a hexavalent vaccine (DTaP-IPV-Hib-HepB) in June 2021. In the study database, a larger proportion of infants received a combination vaccine without hepatitis B (DTaP-IPV-Hib) than with hepatitis B (DTaP-IPV-Hib-HepB). The proportion of infants receiving pentavalent DTaP-IPV-Hib began to decline in the second half of 2021 through July 2022, coinciding with the introduction of the hexavalent vaccine. Therefore, the increase we observed in infants receiving hepatitis-B-containing vaccines likely reflects the transition from a DTaP-IPV-Hib to a DTaP-IPV-Hib-HepB vaccine.

Our findings also align with a 2023 study on vaccination coverage by 24 months of age that reported increased coverage rates for most vaccines for the 2018–2019 birth cohort compared with the 2016–2017 birth cohort [17]. Further, a study comparing vaccination coverage by milestone ages (8, 13, 16, 19, and 24 months) between the pre-pandemic and pandemic periods did not find COVID-19-associated declines in coverage at the national level [52]; however, the most recent birth month included in the analysis was May 2020, and the study’s ability to assess the impact of COVID-19 on the vaccination of children born during the pandemic was therefore limited [52].

It is reassuring that the COVID-19 pandemic least affected the uptake of routine vaccinations in the youngest and most vulnerable age group, but it is concerning that the deficit in MMR vaccination among individuals 0–2 and 4–6 years of age persists, given the recent resurgence of measles in the US and the need for a 95% vaccine coverage rate to maintain community immunity [35]. However, these deficits may have been overestimated due to changes in the MMR vaccination rate during the baseline period; measles outbreaks in late 2018 to 2019 were the likely drivers of higher 2019 vaccine uptake, which may have contributed to a larger percent decrease when comparing data from pandemic years with baseline levels that include data from 2019. When compared with baseline data from 2018 alone, the decreases in the annual accumulated uptake of MMR vaccines were still observed, but to a lesser extent, for individuals 0–2 years of age in 2020 and 2021 and among those 4–6 years of age in 2020, 2021, and 2022.

Among adolescents 9–16 years of age, the greatest decline in vaccination rates was observed for HPV vaccines. Coverage with this vaccine among adolescents was already low before the COVID-19 pandemic; in 2018, coverage was 48.9% for girls and 47.1% for boys, lower than the Healthy People 2020 target of 80% [21,53]. The National Immunization Survey-Teen (NIS-Teen) recently reported that by 2021, 76.9% of adolescents 13–17 years of age had received at least one dose of HPV vaccine, and 61.7% were fully up-to-date [18]; however, the majority of HPV vaccinations among this age group had occurred before the pandemic, and the authors of the study concluded that the full impact of the pandemic on HPV vaccination coverage can only be assessed once more adolescents who were due to be vaccinated during the pandemic have aged into the NIS-Teen sample [18].

Given this slow pre-pandemic progress toward achieving the national target HPV vaccination coverage rates, the decline in HPV vaccination uptake that we observed during the pandemic represents a major setback for public health efforts. The US HPV vaccination deficit could take up to 10 years to overcome, depending on the rate of catch-up effort [33]. Since HPV can cause cancers and other diseases years or even decades after infection, further delays in increasing HPV vaccination rates to target levels could result in increased long-term repercussions for morbidity, mortality, and health care spending. For instance, a 2021 modeling study projected that missed HPV vaccinations could lead to up to 213,926 additional cases of genital warts, 96,839 of cervical intraepithelial neoplasia, and 6,487 of cervical cancer in the US over the long term [38].

Among adults ≥50 years of age, the greatest public health concern to emerge from our analysis was the persistent deficit in the rate of pneumococcal vaccine administration. Invasive pneumococcal diseases, which can be caused by vaccine-preventable strains of Streptococcus pneumoniae, are a major cause of morbidity and mortality among this age group. Reducing the incidence of pneumococcal disease became even more important during the pandemic as health care systems struggled to cope with the combined impact of COVID-19 and other respiratory illnesses including influenza and pneumonia [54,55]. Further, there is initial evidence that pneumococcal vaccination confers a degree of cross-protection against COVID-19 [56,57]. However, as of 2017 only 16.8% of US adults ≥65 years of age had completed a full pneumococcal vaccination series, although 34% had received at least a single dose of vaccine [58].

The vaccination trends observed in the current study provide evidence that individual- and population-level immunity to vaccine-preventable diseases decreased during the COVID-19 pandemic, increasing the risk of infectious disease outbreaks and the overall disease burden for years to come. Proactive efforts to reach individuals of all ages whose routine medical care was negatively affected by the COVID-19 pandemic are needed to equitably increase vaccination coverage rates to the levels necessary for community-level protection, particularly among adolescents and older adults [13,14,59]. A notable finding of our analysis was that the rate of in-person wellness visits recovered faster and more completely than the rate of vaccine administrations in adolescent and adult age groups, indicating that opportunities for individuals to receive scheduled and overdue vaccinations during these visits were potentially being missed. For example, in 2021, individuals 9–16 years of age attended 0.6% more in-person well-child visits than expected based on baseline levels but received 10.0% fewer HPV vaccinations than expected; similarly, individuals ≥65 years of age attended 19.6% more in-person wellness visits than expected but received 42.7% fewer pneumococcal vaccinations. Further work will be necessary to understand whether these missed opportunities are related to increased patient or parental vaccine hesitancy, misinformation, lack of complete and timely patient vaccination data (for example, for individuals moving to a new state or provider network, or undergoing vaccination at a public clinic or other out-of-network facility), lack of vaccination prompts in the immunization information systems (IIS) and electronic health records used by health care providers, provider capacity, or other systemic factors that can impact vaccine uptake. It is also possible that the administration of COVID-19 vaccines or provision of other health services was prioritized over routine vaccinations at in-person wellness visits during the study period. Lastly, among adolescents 9–16 years of age, HPV vaccine administration rates were lower than for meningococcal and tetanus-containing vaccines, which are more commonly required for school entry; it is therefore possible that school-mandated vaccines may have been prioritized over HPV vaccines.

Mechanisms other than routine wellness visits can also be used to promote routine vaccination. Provider, patient, and parent education around the urgency of staying up-to-date with vaccination schedules to prevent infectious diseases and outbreaks is important, potentially coupled with updated vaccination prompting mechanisms in IIS, expanding direct patient and parent access to individual vaccination records through patient portals or apps, and better infection control measures in vaccine administration settings to increase patient and parent confidence in the safety of in-person health care visits [60,61]. For adolescents, expanding state lists of vaccines required for public school attendance and/or introducing stricter exemption policies may assist in increasing vaccine uptake. For example, while most states require DTaP, MMR, polio, and varicella vaccination and a smaller number require meningococcal vaccination, as of 2022, only 4 states and Puerto Rico require proof of vaccination against HPV, the vaccine whose rate of administration among adolescents declined the most in the current analysis [62].

Allowing and promoting the administration of routine vaccinations in more convenient, complementary settings such as pharmacies, mobile clinics, schools, and other community settings, as well as enabling more convenient clinic access such as walk-in/drive-through clinics with extended opening hours, may also aid in short-term catch-up efforts and may prove a sustainable long-term strategy to strengthen vaccination programs [60,61]. Allowing pharmacists and other pharmacy staff (such as interns and technicians) to administer routine vaccines could also improve access to vaccination services, especially in underserved regions and provider deserts, and has been associated with increased vaccine uptake and vaccination prompt opportunities [63–67]. In the longer term, new (and sustained) funding and evidence-based policies to support diverse stakeholder efforts from the local to national level, as well as improved vaccination infrastructure and educational initiatives, will be needed to reimagine post-COVID-19 routine vaccination programs.

This study is subject to some known limitations. First, all claims data are subject to potential omissions and miscoding. In particular, pharmacy claims for vaccine administrations – which may have become more common during the pandemic for some vaccines [68]—were not included, but it would be valuable to evaluate trends in vaccine administration locations in future studies. Second, this was a cross-sectional analysis of monthly vaccine administrations; vaccination coverage rates were not measured, and there were no longitudinal follow-up or continuous enrollment requirements. Third, the study population comprised individuals with commercial insurance through large employers and may not be generalizable to the overall US population, especially during 2020, when US unemployment rates spiked due to the COVID-19 pandemic [69]. The study population likely underrepresents individuals with insurance obtained through small and medium-sized employers, individuals publicly insured with Medicaid and those individuals receiving vaccinations through the Vaccines for Children program, individuals insured via the individual marketplace, adults with no insurance, and the Medicare population. Thus, the current study was likely to overestimate overall US vaccination uptake during the impact period. An additional limitation of our study is that there was no sociodemographic stratification of the data, and we were therefore unable to repeat published analyses that have suggested that the pandemic exacerbated existing racial, ethnic, and socioeconomic disparities in the uptake of routine vaccinations and other forms of preventive care [5,7,26,28].

Other factors may have resulted in over- or underestimations of vaccine administration rates during the study period compared to baseline. As discussed above, the MMR vaccine administration rate was not stable during the baseline period, necessitating separate comparisons to 2018, 2019, and averaged 2018–2019 baseline data. Additionally, the ACIP changed their non-risk-group recommendations for pneumococcal vaccination in adults ≥65 years of age in 2019 from a 2-dose to a 1-dose regimen, unless 2 doses were decided upon during shared clinical decision-making [70]; it is possible that the change to shared decision-making just before the pandemic could have contributed to the pneumococcal vaccine administration deficits that we observed among this age group. For all vaccines, individuals were eligible for inclusion in the analysis if they were enrolled in the study database in any month during the study period. The entry and exit of individuals within a given month could lead to an underestimation of vaccination rates since they would be captured in the denominator, but their vaccine claims would be excluded from the corresponding numerator. The Early View option allowed for near real-time analysis of claims data, but comprised adjudicated claims only, which may introduce lag and underestimate vaccination rates; the partial data we extracted from September to November 2022 were excluded from analysis for this reason. Vaccine administration data from August 2022 may subsequently change as more claims are adjudicated and incorporated into the database. Lastly, the yearly estimates for 2022 were based on only 8 months of data. In previous years, we observed slightly higher rates of vaccine administration later in the year, and thus the incomplete data for 2022 may reflect an underestimation of vaccine uptake, particularly when comparing 2022 cumulative data with the full years of data available for 2020 and 2021.

In conclusion, our updated and expanded analysis of in-person wellness visits and routine vaccinations in the US from January 2020 to August 2022 demonstrates that the vaccination deficits observed earlier in the pandemic have persisted into 2021 and 2022 to varying degrees in all age groups. The better recovery we observed in the rate of wellness visit attendance compared to vaccine administration rates highlights potential missed opportunities to make up for missed vaccinations. The persistent vaccination deficits revealed by this updated analysis necessitate immediate and urgent action to increase vaccination coverage to a level that will provide community-level protection and avoid an increased burden of vaccine-preventable infectious diseases in the years and decades to come.

Declaration of interest

AL Eiden, A DiFranzo, A Bhatti, H Echo Wang, G Bencina, K Saxena, YT Chen, SA Kujawski are current employees of Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, NJ, U.S.A, who may own stock and/or stock options in the Company. L Yao was an employee of Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, NJ, U.S.A during the time of the study. who may own stock and/or stock options in the Company. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or material discussed in the manuscript apart from those disclosed.

Reviewer disclosure

Peer reviewers on this manuscript have received an honorarium for their review work. Peer reviewers on this manuscript have no other relevant financial or other relationships to disclose.

Author contributions

All authors have substantially contributed to the conception and design of the article, interpreting the relevant literature and were involved in writing the review article or revised it for intellectual content.

Acknowledgments

The authors thank Cath Ennis, PhD, in collaboration with ScribCo for medical writing assistance. Jo Wu and Angela Chen from Tigermed for their assistance with data programming. Odysseus Data Services, Inc. as technology partner in dashboard development.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/14760584.2023.2217257

Data availability statement

We have made all monthly percent change data available via an interactive website that allows users to generate visualizations of data of interest. The data can be accessed at https://vaccinationtrends.com.

Additional information

Funding

The manuscript was funded by Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, NJ, USA.