High coverage and timeliness of vaccination of children under 6 years of age in Risaralda, Colombia

ABSTRACT

This study determined the coverage and timeliness of immunization in children <6 y from Risaralda, Colombia. A retrospective cross-sectional study evaluated data from a vaccination coverage and timeliness verification survey conducted in 2019, including 2457 children <6 y from Risaralda, Colombia. Variables included demographics, a record of vaccinations included in the Colombian Vaccination Plan, and date of immunization. Vaccination was defined as timely until 29 d after the day established by the plan. Coverage was over 95% for all vaccinations, except the boosters of diphtheria/pertussis/tetanus (DTP) and oral polio at 18 months (91.0%), influenza (85.6%), and yellow fever (49.2%). Most surveyed children demonstrated very high timeliness of vaccination, with values close to, or over, 90%, although there were exceptions for pentavalent (DTP+Haemophilus influenzae type B+hepatitis B) and polio vaccines at 6 months (79.4%), influenza (85.6%), and yellow fever (49.2%). Before the COVID-19 pandemic, Colombian Vaccination Plan demonstrated high coverage and timeliness of vaccination of children <6 y of age; however, timeliness for the third dose of DTP-Hib-HBV and polio showed opportunities for improvement.

KEYWORDS:

• Colombia
• immunization
• immunization program
• vaccination coverage
• vaccine-preventable diseases
• DTP

Introduction

Childhood vaccination is one of the most cost-effective interventions in public health, and its correct implementation and provision of full access to the population of a country should be a priority. This practice is important to reduce most vaccine-preventable infectious diseases by more than 90%,¹ as reported by studies in the United States after the inclusion of vaccination programs.^2,3 Vaccination programs not only provide a benefit to immunized children but also indirectly benefit the community through herd immunity,⁴ protecting unvaccinated persons (herd effect appears when a large number of people in a population are immunized, decreasing the likelihood of transmission to the rest of the population).⁵ Therefore, the implementation of vaccination programs is of utmost importance, as is identifying the coverage and timeliness of immunization indicators, to assess the program’s capacity and possible opportunities for improvement.

However, a situation that may be problematic for controlling these vaccine-preventable infectious diseases is the increase in cross-border migration into Colombia, since according to reports this population may have lower vaccination rates,⁶ risking the success of public health programs, and creating the need to include this new population in immunization programs to improve coverage.⁷ According to the International Organization for Migration by December 2020, more than 1.7 million Venezuelans lived in Colombia, of which 966,714 (55.9%) were irregular migrants,⁸ and in Risaralda, there were more than 33,000 Venezuelan migrants with residence permits.⁹ It is important to consider the reasons why some parents choose not to vaccinate their children, as this can impact vaccination coverage rates and increase the risk of outbreaks. Reasons for not vaccinating may include concerns about vaccine safety,¹⁰ distrust of healthcare providers or government institutions, religious or philosophical beliefs, or the belief that the vaccine-preventable disease is not a serious threat.¹¹ Understanding and addressing these concerns through education and communication can help increase vaccine acceptance and improve vaccination coverage rates.¹²

In addition, ensuring timely vaccination is critical to achieving maximum protection against vaccine-preventable diseases. Vaccination schedules are designed to provide the most effective protection when vaccines are administered at specific ages or time intervals. Delayed vaccination can lead to increased susceptibility to infections and a higher risk of outbreaks, particularly in vulnerable populations such as young children and the elderly.¹³ To address this issue, it is important to increase awareness among parents and caregivers about the recommended vaccination schedule and the importance of adhering to it. Health care providers can also play a vital role in educating parents and caregivers about the benefits of timely vaccination and the risks of delaying or missing doses.¹⁴ By ensuring that vaccines are administered on time, health systems can maximize the protection provided by vaccines and prevent unnecessary illnesses and deaths^14,15

Reports show quite high coverage for the Colombian Vaccination Plan, reporting coverage of over 90% for traditional vaccines such as Bacillus Calmette-Guerin (BCG), pentavalent (diphtheria, tetanus, whole-cell pertussis, Haemophilus influenzae type B, and hepatitis B), polio, MMR (measles, mumps, and rubella), and less for vaccines introduced in the immunization schedule in the last decade with rotavirus close to 80%, pneumococcal vaccines 77.9%, and influenza 48.4%.¹⁶ Furthermore, there are still problems regarding delays in immunization, which is a potential problem for the program’s success.^17,18

While national statistics show that vaccination coverage (the proportion of children having received a complete schedule of each vaccine out of the total number of children for each age group) in children under 6 y of age is good for most vaccines in Colombia, the timeliness of vaccination (Proportion of children with timely immunization performed in the age range recommended) is not known in detail. The development of a study with a nationally representative sample that describes the coverage and timeliness of immunization in Colombian children under 6 y of age is necessary to fill these knowledge gaps. Therefore, this study aims to determine the coverage and timeliness of immunization in a sample of children under 6 y of age from Risaralda, Colombia, and to identify the main reported reasons for non-vaccination in this group.

Material and methods

In this retrospective cross-sectional study, data from surveys conducted by the Department of Health of Risaralda regarding coverage and timeliness of immunization in 2019 were used. The application of the vaccination coverage survey was carried out by the Departmental Health Secretary of Risaralda, Colombia, according to the sampling recommended by the WHO through conglomerates by blocks according to the size of the municipalities in the urban area. The survey includes both the population with vaccination cards and those without cards. The design of the survey is unique to all of Colombia and mandatory application on an annual basis in each municipality and region of the country. The survey was carried out by trained and certified personnel from the Risaralda Health Secretary, in person at the residences of the selected population in the cluster sample. These surveys were stratified by the size of municipalities. The full methodology has been described elsewhere.¹⁹

This first phase included a preliminary analysis of data from the survey conducted in 2019 in the department of Risaralda, Colombia (n = 2457). The data included children under 6 y of age, from urban areas, of any gender, holding vaccination cards from Risaralda, Colombia, with residence for at least 2 months in the city. Exclusion criteria were not considered.

Data were obtained from the Health Secretary of Risaralda, Colombia, and validated by the research team, looking for inconsistencies (lost data, erroneous or mistyped data), and the following variables were considered in this study:

1. Sociodemographic: age (months), age group (0–11 months; 12–23 months; 24–35 months; 60–71 months), municipality and department of residence, survey date, and ethnicity were recorded.

2. Vaccination: each vaccine included in the Colombian Vaccination Plan (CVP) (see Supplementary Table S1)²⁰ that was registered on the vaccination card of each child was recorded.

3. Vaccination timeliness: receipt of each vaccine was categorized as timely if it was performed in the age range recommended according to the CVP of Colombia (guidelines for evaluation of coverage, timeliness, and completeness of vaccination schedule in Supplementary Table S2). Timeliness of each vaccine was calculated as the proportion of children with timely immunization in relation to the total number of children in that age group.

4. Coverage: the coverage of each vaccine was calculated as the proportion of children having received a complete schedule of each vaccine or group of vaccines (1, 2, or 3 doses), as well as the boosters for those vaccines that required one out of the total number of children for each age group. The proportion of children with completion of all scheduled vaccines in 12–23 months, 24–35 months, and 60-71-months age groups was determined.

5. Reasons for non-vaccination: frequency of non-vaccination (Identification of the absence of a dose of any vaccine that should be applied for the age of the child), and the main reasons reported were described.

From these data, a dataset was constructed and analyzed using the SPSS v26.0 statistical software. Univariate analyses were performed as follows: for categorical qualitative variables, frequencies and proportions were established. For quantitative variables, parametric behavior by the Kolmogorov–Smirnov test was first analyzed, and for those parametric variables, means and standard deviation were presented, and for those non-parametric variables, median and interquartile ranges were provided.

Bioethical considerations

All personal information was handled with strict confidentiality and never had data that could lead to patient identification. The protocol was classified according to Resolution 8430/of 1993 of the Ministry of Health as a non-risk Research. The ethical principles of justice, non-maleficence, beneficence, and confidentiality established by the Declaration of Helsinki were respected. No personal data on any of the subjects were considered. The protocol obtained approval from the bioethics committee of the Universidad Tecnológica de Pereira (Approval code: 01-14-12-20).

Results

A total of 2457 children were evaluated in the 2019 vaccination survey in Risaralda, Colombia. The mean age of the included children was 27.1 months ± 21.4 months (median 21; interquartile range 11–33 months), with similar proportions in age groups 0–11 and 12–23 months and slightly lower in the older age groups (Table 1). Most children were surveyed in Pereira, Dosquebradas, and Santa Rosa de Cabal municipalities (n = 1526; 62.1%), and the remaining 931 children (37.9%) were surveyed in the other 11 municipalities of the department of Risaralda (Table 1), and the largest proportion of children lived in urban areas.

Table 1. Sociodemographic characteristics of 2457 children with a vaccination card surveyed in the department of Risaralda, Colombia, in 2019.

Variable	Frequency (N = 2457)	%	Total population*	Urban population
Age (mean ± SD)	27.1 ± 21.4
0 to 11 months	673	27.4
12 to 23 months	685	27.9
24 to 35 months	591	24.1
60 to 71 months	508	20.7
Municipality
Pereira	651	26.5	467,269	385,838
Santa Rosa De Cabal	441	17.9	77,838	64,267
Dosquebradas	434	17.7	217,178	204,280
La Virginia	112	4.6	27,923	27,189
Mistrató	112	4.6	16,950	3892
Pueblo Rico	112	4.6	16,156	2740
Quinchía	112	4.6	27,292	7209
Belén de Umbría	84	3.4	24,690	12,460
Marsella	84	3.4	16,940	8521
Apia	70	2.8	12,406	5453
Guática	70	2.8	12,158	3558
La Celia	70	2.8	7154	2881
Santuario	70	2.8	12,226	6328
Balboa	35	1.4	6423	1518

*Estimated population for 2019. Source: National administrative department of statistics (https://www.dane.gov.co/index.php/estadisticas-por-tema/demografia-y-poblacion/censo-nacional-de-poblacion-y-vivenda-2018).

All surveyed children were holders of vaccination cards, which were presented to the interviewers. Coverage was over 90% for almost all vaccines, with the exception of seasonal influenza and yellow fever, which had lower proportions (Table 2). Most surveyed children demonstrated a very high timeliness of vaccination, with values close to, or over, 90%, although there were exceptions for pentavalent and polio vaccines at 6 months of age, seasonal influenza first dose and its booster, and yellow fever. Table 2 presents coverage and timeliness data according to the expanded program of immunization of Risaralda.

Table 2. Coverage and vaccination timeliness of the Colombian Vaccination Plan of 2,457 children with a vaccination card surveyed in the department of Risaralda, Colombia, in 2019.

Colombia vaccination plan – Up to 5 y				Coverage		Opportunity
Recommended Age	Vaccine		Dose	(vaccine application/ n group)	%	(timely application/ n group)	%
At birth	BCG		Single	673/673	100	669/673	99.4
	Hepatitis B		At birth	671/673	99.7	671/673	99.7
2 Months	Pentavalent	Diphtheria – Pertussis – Tetanus (DTP)	Initial dose	3-dose schedule		501/549	91.3
		Haemophilus Influenzae type B (Hib)
		Hepatitis B
	Oral Polio		Initial dose	3-dose schedule		501/549	91.3
	Rotavirus		Initial dose	2-dose schedule		501/549	91.3
	Pneumococcal		Initial dose	3-dose schedule		501/549	91.3
4 Months	Pentavalent	Diphtheria – Pertussis – Tetanus (DTP)	Second dose	3-dose schedule		387/440	88
		Haemophilus Influenzae type B (Hib)
		Hepatitis B
	Oral Polio		Second dose	3-dose schedule		387/440	88
	Rotavirus		Second dose	482/497	97	387/440	88
	Pneumococcal		Second dose	482/497	97	387/440	88
6 Months	Pentavalent	Diphtheria – Pertussis – Tetanus (DTP)	Third dose	355/374	95	255/321	79.4
		Haemophilus Influenzae type B (Hib)
		Hepatitis B
	Oral Polio		Third dose	355/374	95	255/321	79.4
	Seasonal influenza		Initial dose	321/374	85.6	321/374	85.6
12 to 23 Months	Seasonal influenza (booster between 12–23 months of age)		Second dose	62/685	9	62/687	9.0
12 Months	Measles – Mumps – Rubella (MMR)		Initial dose	670/685	98	444/472	94.1
	Varicella		Initial dose	670/685	98	647/685	94.3
	Pneumococcal		Booster	670/685	98	444/472	94.1
	Hepatitis A		Single	670/685	98	467/472	98.9
18 Months	Diphtheria – Pertussis – Tetanus (DTP)		First booster dose	333/365	91	629/706	89.1
	Oral Polio		First booster dose	333/365	91	629/706	89.1
	Yellow fever (YF)		Single	337/685	49.2	337/685	49.2
60 Months	Diphtheria – Pertussis – Tetanus (DTP)		Second booster dose	483/508	95	305/332	91.9
	Oral Polio		Second booster dose	483/508	95	305/332	91.9
	Measles – Mumps – Rubella (MMR)		First booster dose	483/508	95	305/332	91.9
	Varicella		First booster dose	ND	ND	ND	ND

We identified that 69.5% (n = 476) of children between 12 and 23 months, and 68.7% (n = 406) of children between 24 and 35 months of age had a complete vaccination schedule, this value increases to 98.0% (n = 670 among 685 children in the first group) if the seasonal influenza vaccine is excluded. For 60–71-month-old children, 95.0% (n = 483 of 506 children) were found to have had all boosters.

Finally, 93 (3.8%) children were identified with a reason for non-vaccination (these answers are from those caregivers who explained some reason for not vaccinating a certain dose). Recorded reasons for lack of vaccination can be seen in Table 3, the most common causes are those related to problems of the caregiver or family (84.9%).

Table 3. Reasons for non-vaccination in 2457 children with a vaccination card surveyed in the department of Risaralda, Colombia, in 2019.

Reasons for non-vaccination	Frequency (N = 2457)	%
Children with a missing a dose	93	3.8*
Logistical problems	7	7.5
Lack of vaccine at the vaccination center	5	5.4
Distant vaccination site	1	1.1
Social Security affiliation problems	1	1.1
Health problems of the child at the time of vaccination	7	7.5
Acute illness of the child	6	6.5
Prior adverse reactions to the vaccine	1	1.1
Caregiver related problems	79	84.9
Lack of caregiver time	59	63.4
Vaccine rejection	2	2.2
Caregiver claims to have the “complete scheme”	18	19.4

*of the total population.

Discussion

The present study was carried out in Risaralda, in the central-western region of Colombia, a department with a high proportion of inhabitants living in urban centers, with access to public services and a higher development index compared to the average of the country.²¹ It was possible to identify that the coverage and timeliness of immunization were both over 90% for most vaccines, except influenza and yellow fever, demonstrating the effectiveness of the department’s vaccination plan, and create a baseline for future estimates of these indicators in the country pre-and post-COVID-19 pandemic.

A similar study, performed in Colombia in 2012 by Narvaez et al., identified an absolute coverage of over 90% in 80 different municipalities for most vaccines, with the exception of rotavirus and influenza.¹⁶ This is similar to the findings in this study for the lower coverage for seasonal influenza, but not for rotavirus vaccine, which exceeded 97%. This difference can be explained by the complete inclusion of this vaccine in the CVP after 2009, and its greater awareness and availability of vaccination points.²²

During 2019, in the department of Risaralda, timeliness of immunization was over 80% for almost all biologics, with many over 90%. This varies from that reported by Narvaez et al. during 2012, in which only BCG and hepatitis B at birth had more than 85% with timely immunizations, with all other vaccines having between 50% and 70% timeliness of immunization. While the data provided by Narvaez et al. ⁶ originated in a different period of time and at a local level, the disparities in timeliness of vaccination between these studies may indicate two situations: that there may be an increase in vaccination compliance rates, or that there is heterogeneity of this indicator at the national level. Heterogeneity is also suggestive of a problem of equity, which has been widely reported in both low- and high-income countries.^23–25 Another analysis of multiple studies carried out by Newcomer et al. in the United States identified that by 2017 about 68% of children received all doses on time,¹⁴ a situation that has increased because a 2005 report in this same country identified that 48% had the applications on time.²⁶

Recently, there have been logistical advances in the CVP of Colombia and Risaralda in particular, which can be added to its greater economic development,²⁷ and increased access to health services.²⁸ This may facilitate availability of immunization, leading to greater coverage and more timely vaccination in the pediatric population, compared to previous studies published in Colombia. However, these results need to be evaluated at a national level.¹⁶

For immunization teams in any country, achieving high vaccination coverage is a priority, but this must be accompanied by timeliness in its implementation to guarantee the true protection that the vaccine provides. While this study population derives from a department with approximately a million inhabitants,²¹ differences between coverage and timeliness were few, except for diphtheria-pertussis-tetanus third dose (DTP3) with a difference of 15%. Other studies from Colombia and other countries have shown that this difference can be over 50%,^16,29 putting children under 2 y of age at particular risk of developing vaccine-preventable diseases, and increasing the likelihood of outbreaks of these infections.³⁰ This 15% mismatch between timeliness and coverage rates for DTP3 indicates that over a period of time, 20% of infants are exposed to an increased risk of contracting the diseases. For the specific case of pertussis, it has been shown that it is of great importance to administer vaccine doses within the established timelines, especially in infants who are at greater risk of severe disease.³¹ This difference between vaccination coverage and timeless that has been observed in several countries, regardless of their income level and health system, and, unlike this study, not only for DTP but for other vaccines in the pediatric calendar.^32–34

Several publications support vaccination as one of the safest and most cost-effective public health interventions that saves millions of lives.^35–37 Studies have shown that the economic benefits of vaccination include reduced healthcare costs, increased productivity, and improved quality of life for individuals and communities. For instance, a 2014 study conducted in the United States by Zhou et al. estimated that every dollar spent on childhood vaccinations generates up to $5.30 in societal benefit, including $3.50 in direct healthcare savings and $1.80 in productivity gains.³⁸ Another study, published by Toor et al., estimates that it has prevented the deaths of 97 million people, considering the pre-COVID-19 era, between 2000 and 2030,³⁹ which makes this activity one of the priorities of any health system, and it is essential to increase coverage and timeliness of immunization. However, it is important to highlight that this analysis is conducted with data from 2019, prior to-COVID-19, and these results can potentially change due to the difficulty of access to vaccines during quarantines and other situations occurring during the pandemic, which are not yet fully established,^40–43 These findings highlight the importance of continued investment in vaccination programs to improve health outcomes and reduce economic burden for health systems.

Unfortunately, in this study, reasons for non-vaccination were only identified in 3.8% of children, despite the fact that vaccines such as seasonal influenza had low coverage levels. Among the reasons, it was identified that the most frequent problem for not going to the health service after immunization is related to the caregiver, due to lack of time or misinterpretation of information regarding the next doses of vaccines, similar to what has been found in other studies.^16,44 Only two cases were recorded whose reason to explain the lack of vaccination was the rejection of the vaccine, a reason that has been very common in other countries such as the United States⁴⁵ and countries in Europe.⁴⁶

The vaccination program in Colombia has been highly effective, as shown by the statistics of the National Institutes of Health for 2019, with only one case of diphtheria and 162 cases of measles in the country, with none in Risaralda, and 94% of all cases were imported or related to an imported case from another territory.⁴⁷

This study presents some limitations, such as the use of an annual and routine survey performed by the health services of Risaralda, which collects information registered on vaccination cards of children. This could potentially not show the reality of vaccination and under-estimate the coverage compared to records of health centers that are digitally stored. In addition, by only evaluating those children with a card in urban areas, the results may be overestimated in comparison with rural or migrant populations. Furthermore, this analysis only has information from one department or region of Colombia and with a relatively small sample size; therefore, conclusions would not necessarily be representative for other populations with a different sociodemographic context, such as the inhabitants of the border regions of the country. It is possible that studies in different countries outside the Pan-American Health Organization have different mechanisms to establish coverage measurement and timely application. It is recommended to carry out new studies against reasons for non-vaccination, especially with the influenza and yellow fever vaccine, which present a lower coverage than expected.

Conclusions

In conclusion, in the department of Risaralda, Colombia, timeliness of immunization is very high, and coverage for most vaccines for the population under 60 months of age is over 90%, which can guarantee high protection against vaccine-preventable infections in the region. There were also some problems identified and reasons for non-vaccination that can be useful for designing strategies to improve the CVP.

Author contributions

Conceptualization: JEMA and MEMD.

Methodology: JEMA, MEMD, and JCVZ.

Validation: JEMA and MEMD.

Formal analysis: JEMA and MEMD.

Investigation: JEMA, MEMD, and JCVZ.

Data curation: JEMA and MEMD.

Writing original draft: JEMA and MEMD.

Resources: JCVZ.

All authors contributed to the writing of the manuscript and the revised drafts.

Availability of data materials

Protocolos.io. Data access: dx.doi.org/10.17504/protocols.io.kxygxznmkv8j/v1.

Institutional review board statement

All personal information was handled with strict confidentiality and never had data that could lead to patient identification. The protocol was classified according to Resolution 8430/of 1993 of the Ministry of Health as a non-risk Research. The ethical principles of justice, non-maleficence, beneficence, and confidentiality established by the Declaration of Helsinki were respected. No personal data on any of the subjects were considered. The protocol obtained approval from the bioethics committee of the Universidad Tecnológica de Pereira (Approval code: 01-14-12-20).

Disclosure statement

JCVZ is a Sanofi employee and may hold shares and stock options in the company; JMA, and MMD have no conflict of interest.

Supplementary data

Supplemental data for this article can be accessed on the publisher’s website at https://doi.org/10.1080/21645515.2023.2257424.

Additional information

Funding

This collaborative work with Universidad Tecnológicade Pereira was funded by Sanofi [under Grant:ID PER00095]. Sanofi did not participate in the management or data analysis of the study data.