https://orcid.org/0000-0003-2765-4488
ABSTRACT
Maternal vaccination against pertussis is safe and provides effective protection against pertussis for the newborn, but the vaccine coverage rate remains generally low. Norway is currently planning for introduction of routine maternal pertussis vaccination. To assess maternal pertussis vaccination acceptance among pregnant Norwegian women, we surveyed women at 20–40 weeks gestation in 2019. Among the 1,148 pregnant women participating in this cross-sectional study, 73.8% reported they would accept pertussis vaccination during pregnancy if it was recommended, 6.9% would not accept and 19.2% were undecided. Predictors for low likelihood of accepting pertussis vaccination during pregnancy included low confidence in health authorities and in maternal pertussis vaccination safety and effectiveness, low awareness and adherence to influenza vaccination during pregnancy, and low awareness of pertussis vaccination. The major reasons reported for not accepting or being undecided about maternal pertussis vaccination were lack of information on vaccine safety for both mother and child. Most women reported that they would consult their general practitioner or a midwife for information if they were offered maternal pertussis vaccination. General practitioners and midwives were also regarded as the most trustworthy sources of information if the women were in doubt about accepting vaccination. We conclude that information addressing safety concerns and raising awareness about maternal pertussis vaccination could increase acceptance of maternal pertussis vaccination. Our findings highlight the pivotal role of the antenatal and primary health care services in providing such information to pregnant women.
Introduction
Pertussis remains a serious health concern worldwide,Citation1 especially for infants who bear the greatest disease burden. Infant pertussis often leads to hospitalization and severe disease can result in death.Citation2–4 Currently available vaccines against pertussis are neither recommended for neonatal use, nor effective in protecting newborn against severe pertussis.Citation5 However, infant protection can be obtained by placental transfer of maternal antibodies during pregnancy. Recent studies show that maternal pertussis vaccination during the second or third trimester is safe and effective, both for the infant and for the mother.Citation6–8 It may also reduce the risk of infant pertussis by direct protection of the mother, who is among the main sources of infection for infants.Citation9 Maternal vaccination is currently considered the best intervention to prevent pertussis in young infants,Citation10 and many countries have already introduced maternal vaccination against pertussis.Citation11 Norway is planning for introduction of routine maternal pertussis vaccination during 2024.
The Childhood Immunization Programme in Norway (CIP) is administered by municipal child health clinics and school health services and currently has coverage rates around 95% for all vaccines.Citation12 Pertussis vaccination has been offered in the CIP since 1952. The current schedule for pertussis vaccination is at 3, 5 and 12 months of age, with booster doses at ages 7 and 12 years.Citation13 The pertussis incidence dropped after CIP introduction of pertussis vaccination, but the incidence has increased in some age groups in recent decades.Citation14,Citation15 A resurgence of pertussis, despite high vaccine coverage, has also been observed worldwide.Citation1 Norway is among the European countries with the highest reported incidence of pertussis,Citation16 likely indicative of widespread access to diagnostics and care as well as mandatory reporting to the Norwegian Surveillance System for Communicable Diseases (MSIS).Citation17
Maternal vaccination against influenza and COVID-19 has been recommended in Norway since 2009 and 2021, respectively, but the vaccination coverage during pregnancy is unknown. Unfortunately, maternal vaccination coverage is poorly documented in most countries, but it generally appears suboptimal, regardless of the vaccine offered.Citation18–20 Several barriers to maternal vaccination have been identified in recent reviews.Citation21–23 Safety concerns, particularly relating to the child, seem widespread and related to lower maternal vaccine uptake. Moreover, complacency regarding the risk of infection and the perceived severity of the disease, lack of knowledge, logistical constraints and prior vaccine refusal may also be associated with lower maternal vaccination uptake. On the other hand, trust in the effectiveness and safety of maternal vaccination and receiving a recommendation for vaccination from a healthcare provider strongly promotes maternal vaccination. Similar barriers and facilitators have been identified in single studies focusing on intentions for maternal vaccination against pertussis.Citation24–26
The main objective of the present study was to identify predictors of acceptance of maternal pertussis vaccination among pregnant women in Norway. We also assessed their reasons for non-acceptance, information needs and preferred information sources regarding maternal pertussis vaccination.
Methods
Study population
Participants were recruited through a Facebook/Instagram advertisement targeting women who, according to provider information, were aged 18–45 years, resided in Norway and had shown an interest in pregnancy, childbirth or infants. The advertisement briefly introduced the theme and intent of the study, i.e. to survey women who were 20–40 weeks pregnant on infant pertussis and its prevention. The women could answer the survey electronically through a link in the advertisement that led to the introductory page of the questionnaire, which included a request for active consent to participate in the survey.
There were approximately 55.000 births in Norway in the survey year.Citation27 We aimed to recruit 1000 survey participants, which gives an acceptable margin of error of 3% at the 95% confidence level. The advertisement reached 89.136 IP addresses (i.e. persons). A total of 2,178 persons clicked on the survey link in the advertisement, and a total of 1,148 women completed the survey. All participants confirmed they were 20–40 weeks pregnant (mean ± SD gestation week: 29.4 ± 5.9). We did not give any incentives or compensation for participation. The web questionnaire design and data collection were performed by the analysis agency Respons Analyse. The survey opened on 25 November 2019. By 3 December 2019, we had reached the targeted number of participants and terminated the data collection.
Survey items and measures
The survey focused on pertussis/pertussis vaccination and included additional items on participant demographics/pregnancies/vaccination history (Supplementary 1). Participants were allowed to proceed by skipping single items if they did not want to leave a response. No items were skipped by more than 34 participants. Most items had categorical answer options and included a “don’t know” option. Most items on knowledge and attitudes presented answer options on a symmetrical 5-point scale, ranging from “strongly disagree” to “strongly agree.” For the analyses, we dichotomized such 5-point items into “agree” (consisting of the positive sentiments “somewhat agree” and “strongly agree”) and “disagree” (consisting of the negative/neutral sentiments “strongly disagree,” “somewhat disagree” and “neutral”), and kept the “don’t know” answer option as a separate category.
The dependent variable in our main analysis was the answer to the question “If pertussis vaccination for pregnant women was recommended now, would you accept the offer of vaccination?,” to which the participants could respond “yes,” “no” or “don’t know.” To contrast those expressing an unequivocal acceptance to be vaccinated from those who did not, we dichotomized these answer options into “yes” and “no/don’t know” for the analyses.
Most questions allowed only one answer, except questions on information sources, where the participants could list all sources relevant to them, and the question on reasons for not accepting or being undecided about maternal pertussis vaccination, where they could list up to three reasons. The total number of participants may vary by analysis because the number of participants who chose not to answer may differ between items. Moreover, presentation of some items was conditioned on previous responses.
Statistics
All descriptive and model estimates were weighted by iterative proportional fitting using the survey package in R.Citation28 The estimates were weighted for maternal age (≤35, >35 years old), parity (nulliparous, parous), highest attained education level (primary/secondary/vocational school, university/college) and region of residence (Southeast, West, Mid, North), with corresponding general population estimates obtained from the Medical Birth Registry and Statistics Norway (see ). Weighted generalized linear binomial models with a logarithmic link were employed to obtain relative risk (RR) estimates with associated 95% confidence intervals (CI) of accepting vaccination versus not accepting or being undecided about vaccination. The models were adjusted for trimester (second, third), since gestational age may be associated with maternal vaccine acceptance.Citation29 Estimates from the most parsimonious model are presented. Statistical tests were two-tailed with an alpha level of 0.05. Descriptive statistics are given as weighted sample sizes and percentages. Statistical computing was done in R version 4.3.0.Citation30
Table 1. Characteristics of the study cohort and the general population.
Ethics
All participants actively provided informed consent to participate in the survey. The consent was given electronically. The study followed the requirements of the Personal Data Act. We did not have access to personally identifiable information. The study did not require ethical review board approval because it does not fall within the jurisdiction of the Health Research Act.
Results
shows the unweighted and weighted study population sample size by sociodemographic characteristics. Most women in the study population were younger than 35 years old, lived in the Southeastern part of Norway and had attended university/college. The study population was similar to the general population of women who gave birth in 2019 in terms of maternal age and region of residence but was overrepresented by nulliparous women and women with university/college education.
Forty-two percent of the women reported that they had attended prenatal checkups by the midwife only, while 47.6% reported that they had attended both at the midwife and at the general practitioner. The remaining women reported that they had attended prenatal checkups at the general practitioner only (9.4%), or at an unspecified other location (0.9%).
Of the 1,148 pregnant women participating in the study, 847 (73.8%) agreed to the statement: “If vaccination against pertussis during pregnancy was offered now, would you accept the offer?,” while the remaining participants answered that they would not have the vaccine (N = 80 (6.9%)) or that they did not know (N = 221 (19.2%)).
Awareness of pertussis
A total of 1,101 (95.9%) of the women had heard of pertussis, while 47 (4.1%) women had not heard of or did not know whether they had heard of pertussis. Moreover, 74.3% and 63.3% would have the pertussis vaccine if it was offered to them during pregnancy among those who had heard of and those who had not heard of pertussis, respectively. However, this difference in acceptance fell short of statistical significance (RR (95% CI): 0.85 (0.63 to 1.15), ). There was a trend that women who were unaware of or had lower risk perceptions regarding pertussis (in terms of prevalence, transmissibility, susceptible age, severity for infants and severity for pregnant women) were less accepting of maternal pertussis vaccination than women who had higher risk perceptions, but these differences did not reach statistical significance ().
Table 2. Awareness and perceptions regarding pertussis and pertussis vaccination, by intention to be vaccinated against pertussis during pregnancy1.
Awareness of pertussis vaccination
Approximately one fifth of the participants answered “don’t know” to each of three questions regarding awareness of pertussis vaccination, i.e., whether: (i) pertussis vaccination is offered in the childhood vaccination program, (ii) a booster is recommended every 10 years for adults, and (iii) infants are poorly protected against pertussis until they are vaccinated at three months of age. Compared to women who confirmed these statements, women who answered “don’t know” were significantly less likely to accept vaccination against pertussis during pregnancy, with a difference in acceptance rate exceeding 10% points for each question (RR (95%CI): (i) 0.80 (0.70 to 0.91); (ii) (0.86 (0.76 to 0.98); (iii) (0.85 (0.76 to 0.95); ). Moreover, women who answered “no” to each of these questions also tended to be less accepting of vaccination against pertussis during pregnancy, but the effect was significant for statement (iii) only (). Specifically, a total of 687 women did, and 161 women did not, think infants were poorly protected against pertussis until they are vaccinated at three months of age, of which 544 (79.2%) and 105 (65.1%) women, respectively, were accepting of vaccination against pertussis during pregnancy (RR (95% CI): 0.82 (0.71 to 0.95), ), indicating that pertussis risk perception is associated with maternal pertussis vaccination acceptance.
Perceptions of maternal pertussis vaccination
Women who disagreed to the statement “I worry that my newborn child will get pertussis” were significantly less likely to accept pertussis vaccination during pregnancy than were women who agreed (RR (95% CI): 0.87 (0.80 to 0.94), ). Low confidence in maternal pertussis vaccination effectiveness for protecting against severe pertussis for the child or for the mother was also associated with significantly lower likelihood of accepting pertussis vaccination during pregnancy (RR (95% CI): 0.74 (0.63 to 0.87); 0.77 (0.64 to 0.93), respectively). Low confidence in maternal pertussis vaccination safety was another strong predictor of low maternal pertussis vaccination acceptance. Women who agreed that maternal pertussis vaccination may increase the risk of birth defects or increase the risk of complicated pregnancy were less likely to accept vaccination against pertussis during pregnancy than were women who disagreed (RR (95% CI): 0.58 (0.43 to 0.80); 0.74 (0.56 to 0.96), respectively). Similarly, women who disagreed that pertussis vaccination is safe for pregnant women or disagreed that the benefits of maternal vaccination outweigh the risks, were less likely to accept maternal pertussis vaccination compared to women who agreed (RR (95% CI): 0.62 (0.51 to 0.74); 0.68 (0.57 to 0.80), respectively). A striking finding was the high proportion of women who reported that they did not know whether they agreed or disagreed to each of the four statements regarding maternal pertussis vaccination safety (range 47.6% to 58.0% of the participating women). These women also had significantly lower likelihood of accepting maternal pertussis vaccination compared to women who had confidence in maternal pertussis vaccination safety, although the effect size always was somewhat smaller than for corresponding comparisons for women who explicitly reported low confidence in maternal pertussis vaccination safety ().
Low confidence in health authorities was a strong predictor of low maternal pertussis vaccination acceptance. Among the 122 women who disagreed to the statement “I trust that the health authorities make thorough assessments about the safety of maternal vaccination,” only 46 (37.9%) accepted vaccination against pertussis during pregnancy, compared to 753 out of the 947 women (79.5%) who agreed to the statement (RR (95% CI): 0.48 (0.35 to 0.65), ).
Other vaccination programmes
Not being aware that the Norwegian health authorities recommend maternal flu vaccination, not having been recommended maternal flu vaccination by GP/other health personnel during the current pregnancy, and not having been vaccinated against flu during the current pregnancy were all associated with a significantly lower likelihood of accepting maternal pertussis vaccination (). Moreover, women who did not hold a positive attitude to the CIP were far less likely to accept maternal vaccination against pertussis than were women with a positive attitude to the CIP. This comparison produced the largest effect size observed in the present study (RR (95% CI): 0.31 (0.15 to 0.65)). Own vaccination history in the CIP was also associated with maternal pertussis vaccination acceptance, but the difference in acceptance between women who were and women who were not vaccinated as recommended by the CIP fell just short of significance ().
Table 3. Childhood and influenza vaccination, by intention to be vaccinated against pertussis during pregnancy.1
Reasons for hesitancy
The most frequently reported reasons for not accepting or being undecided about accepting maternal pertussis vaccination were worries about harm for the child, lack of knowledge about consequences of vaccination for the mother, and lack of knowledge about consequences of vaccination for the child, which each was reported by at least 60% of the 301 non-accepting women. Worries about side effects for the mother was reported as a reason for hesitancy by 25.6% of the non-accepting women, while “the vaccine has no effect,” “fear of syringes” and “too many components in the vaccine” each was reported by less than 10% of the non-accepting women ().
Table 4. Pertussis vaccine hesitancy, information needs and sources among pregnant women in Norway.1
Information
When asked about the most needed information if maternal pertussis vaccination was recommended, 82.1% and 80.6% of the participating women reported “side effects for fetus/child,” and/or “consequence of pertussis for the child,” respectively. Some participants also reported need of information on “the effect of the vaccine” (37.2%), “consequence of pertussis for mother” (31.4%), “side effects for mother” (23.9%) and “ways of transmission” (19.6%) ().
The main sources of information that the participants would turn to if maternal pertussis vaccination was recommended were the midwife (81.0%), general practitioner (76.0%), health authority web pages (55.7%) and “internet search” (18.7%). No other information source was reported by more than 10% of the participants (). Similarly, the most frequently reported trustworthy information sources were general practitioner (78.3%), midwife (77.3%), health authority web pages (54.4%) and public health nurse (14.9%) ().
Discussion
Our study aimed to explore the intentions of pregnant Norwegian women to accept pertussis vaccination during pregnancy, and to provide insights into factors that may influence acceptance or hesitancy. We found that a substantial majority of the surveyed pregnant women (73.8%) would accept pertussis vaccination during pregnancy if recommended, which is encouraging for the forthcoming recommendation of this vaccination as part of routine maternity care. However, a notable fraction expressed uncertainty about their decision, and the acceptance rate observed is in the lower range of what has been reported in studies on maternal pertussis vaccination intentions from other countries.Citation24–26,Citation31
We identified several predictors associated with maternal pertussis vaccination acceptance. One striking predictor was trust in health authorities. Low trust in health authority assessments regarding maternal vaccination safety was strongly associated with a reduced likelihood of accepting pertussis vaccination during pregnancy, which is in line with previous research showing that institutional trust is associated with vaccine hesitancy.Citation32 Since only a small minority of the pregnant women surveyed expressed low trust in health authorities in our study, it may currently have limited impact on uptake. However, many countries have witnessed a decline in vaccine confidence.Citation33 This emphasizes need for continued efforts to uphold institutional trust and prevent a rise in vaccine hesitancy. Adequately addressing parental concerns and providing transparent, evidence-based information is likely to play an important role in building and maintaining this trust. Extensive surveillance of all effects of the programme, including its coverage, effectiveness and safety, will also be of great importance.Citation34 Knowledge from surveillance can inform parents about the concerns they report here and can thus instill trust. Quality assurance through surveillance also provides information for further optimization of the programme.
Another predictor for maternal pertussis vaccination acceptance was awareness and adherence to existing vaccination programs, particularly influenza vaccination during pregnancy. Women familiar with and adherent to influenza vaccination exhibited higher acceptance rates for maternal pertussis vaccination. Moreover, not holding overall positive views on the CIP was strongly associated with reduced maternal pertussis vaccination acceptance. These findings indicate an interplay of vaccine acceptance and uptake across vaccination contexts, as also recently demonstrated in the UK.Citation35 Promotion of new vaccine interventions, like maternal pertussis vaccination, could thus be leveraged by introduction within the context of existing successful vaccination programs. We also observed that complacency, i.e., a low-risk perception of infant pertussis, was associated with reduced acceptance of maternal pertussis vaccination. However, in contrast to a previous report,Citation29 gestational age (trimester) was not associated with acceptance in any of our analyses.
Lack of knowledge about maternal pertussis vaccination was common and was often associated with lower vaccine acceptance. This was especially pronounced in perceptions related to vaccine safety, where more than half of the survey participants were nescient. Moreover, issues related to maternal pertussis vaccination safety were by far the most frequently reported reasons for not accepting or being undecided about maternal pertussis vaccination. Previous studies on maternal vaccine acceptance have shown that safety concerns are among the strongest barriers to uptake,Citation21–23 and we observed a similar effect. Particularly low acceptance of pertussis vaccination during pregnancy was observed among women who agreed that maternal pertussis vaccination may increase the risk of birth defects and among women who disagreed that it is safe for pregnant women to get vaccinated against pertussis. Furthermore, although less pronounced, we observed that low confidence in maternal pertussis vaccine effectiveness was associated with reduced acceptance of maternal pertussis vaccination. We do not know why some women deemed pertussis vaccination during pregnancy as unsafe or ineffective despite the evidence that it is generally safe and effective.Citation6–8 However, these findings, and the high proportion of pregnant women who were unaware about the safety of maternal pertussis vaccination, clearly demonstrate a need for additional information on maternal vaccination safety. Moreover, side effects of vaccination for the child, and consequences of pertussis for the child were explicitly reported as the most needed information topics if maternal pertussis vaccination was recommended.
Previous studies have shown that receiving vaccine recommendations from health care personnel is crucial for maternal vaccination uptake.Citation36 Maternal vaccination programmes should take advantage of this prominent position of maternal care providers in the parents’ vaccine decision-making process.Citation37 According to the pregnant women in our study, midwives and general practitioners will be the most important and the most trusted sources for information on maternal pertussis vaccination. This highlights the pivotal role these professions will play for successful maternal vaccination in the Norwegian context, where pre-natal care mainly is given as part of primary health care. It also highlights the importance of training of these maternal care providers so that they can inform and counsel parents adequately with respect to maternal vaccination.
Our findings regarding predictors of maternal pertussis vaccination acceptance are encompassed by the suggested root causes of vaccine readiness.Citation38–41 Moreover, they generally align with broad trends observed in the literature on acceptance and uptake of maternal vaccination,Citation21–23 including against pertussis. The acceptance rate of maternal pertussis vaccination observed in the present study is comparable to that observed in studies from other countries, albeit at the lower end of the range.Citation24–26,Citation31 Differences in acceptance between studies may reflect differences in for instance study design, social norms and background incidence of pertussis. The extent to which each psychological component of vaccine readiness may challenge acceptance, and the ways in which challenges are best met to optimize uptake, may also vary between populations and vaccination contexts. In Norway, a pertinent challenge before the launch of the maternal pertussis vaccination programme is low awareness among pregnant women regarding most issues related to maternal pertussis vaccination.
Strengths and limitations
A limitation of the present study is that we cannot estimate the response rate since we do not know how many eligible women were reached by the Facebook/Instagram advertisement. Moreover, recruitment through social media introduces sampling bias since all eligible individuals do not use social media. However, it is worth noting that Facebook and Instagram are widely used in Norway, particularly among adult women. Among women aged 18–29 or 30–39 years, 87% and 90% had a Facebook account, and 93% and 72% had an Instagram account, respectively, during the recruitment period of the present study, and daily use was reported among 83% and 65% of Facebook and Instagram account owners, respectively.Citation42 However, access to eligible individuals may also be limited by algorithmic filtering and privacy settings. Social media users may also have high resistance to act on invitations e.g. due to information fatigue or data safety concerns, leading to low survey engagement. These features challenge the representativeness of the study sample. Non-response bias, i.e. the tendency for certain groups to be more likely than others to respond to surveys, is also likely to limit the representativeness of the present study sample. For example, immigrants with limited knowledge of Norwegian are likely to be underrepresented because the survey was available in Norwegian only. We addressed lacking representativeness analytically by weighting and adjustment for potential confounders, which is a strength of the present study. Our study also had a relatively high sample size and an acceptable margin of error. Moreover, very few participants skipped single questions, which indicates that few women experienced difficulties completing the survey and that item non-response is unlikely to have influenced our results.
A limitation common to surveys is social desirability bias. In the context of the present study, social desirability bias may have led to an overreporting of maternal vaccination acceptance or, more generally, of behaviors perceived as healthy or compliant to health authority recommendations. We applied several measures to minimize this bias, such as ensuring participants that their responses were anonymous, wording questionnaire items neutrally, and by addressing it in the survey instructions. A further limitation of this study is that we ask for the participants’ intention to get vaccinated in a hypothetical situation where pertussis vaccination is offered during pregnancy, and we don’t know to what extent their answers reflect what their choice would have been if they encountered this situation in real life. However, assessment of hypothetical acceptability can inform public health decision-making and future maternal vaccination programme implementation by identifying barriers to uptake as well as actionable policy and programmatic components, which gives the study high public health relevance. The study is also limited by only surveying pregnant women, and not their partners, who also could weigh in on childhood vaccination decisions.Citation43 Furthermore, the study was performed before the COVID-19 pandemic, and we do not know whether this experience may have impacted on willingness. Reassuringly, the coverage rates of the CIP vaccines have remained high during and after the pandemic,Citation12 thus the parental willingness to have their children vaccinated does not appear affected by the pandemic experience in Norway. A final limitation is that pregnancy status was self-reported, which may have led to inclusion of ineligible participants. During recruitment, we minimized this risk by repeatedly stating that the survey targeted women 20–40 weeks pregnant. Moreover, we explicitly asked for gestational age in the questionnaire, which confirmed that all participants were at this gestational stage.
Conclusion
The study provides actionable insight for the implementation of maternal pertussis vaccination. Although most pregnant women would accept maternal pertussis vaccination, many were undecided. Moreover, many women had low awareness of pertussis and pertussis vaccination, particularly relating to vaccine safety, and low awareness was associated with low acceptance. This highlights a significant requirement for information provision to pregnant women regarding maternal pertussis vaccination, which will enable them to make an informed choice regarding vaccination. Moreover, it suggests a potential for achieving a higher maternal pertussis vaccination uptake rate than the accepting proportion observed in our study, as those who are undecided may demonstrate flexibility in their vaccination decisions.Citation44 Once the maternal pertussis vaccination programme is launched in Norway, surveillance of coverage and engagement with the target population, midwives, general practitioners and obstetricians will be important to assess its performance and to inform further adaptations of the intervention. Randomized controlled trials may also provide evidence about the effect of new interventions that may improve maternal vaccine acceptance and coverage.
Author contributions
Bo T Hansen: Methodology, Data curation, Formal analysis, Validation, Visualization, Writing – original draft, Writing – review and editing
Brita A Winje: Conceptualization, Methodology, Validation, Writing – review and editing
Jeanette Stålcrantz: Conceptualization, Methodology, Project administration, Writing – review and editing
Margrethe Greve-Isdahl: Conceptualization, Methodology, Writing – review and editing
Ethical approval
All participants actively provided informed consent to participate in the survey. The consent was given electronically. The study followed the requirements of the Personal Data Act. We did not have access to personally identifiable information. The study did not require ethical review board approval because it does not fall within the jurisdiction of the Health Research Act.
Supplementary1_pertussis_questionnaire.pdf
Download PDF (360.6 KB)Acknowledgments
We wish to thank Jana Prattingerová for help with development of the questionnaire items.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Data availability statement
The dataset and analysis script are available upon reasonable request to the corresponding author.
Supplementary material
Supplemental data for this article can be accessed on the publisher’s website at https://doi.org/10.1080/21645515.2024.2361499
Additional information
Funding
References
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