Vaccination Card Availability and Childhood Immunization in Senegal

"...interventions designed to improve the retention of child immunization cards may help improving timely childhood vaccination coverage..."

In developing countries, quantitative surveys conducted to estimate childhood vaccination coverage rely on maternal recall when mothers are unable to present their child's vaccination card to interviewers. Using secondary analysis of the 2017 Demographic and Health Survey (DHS) conducted in Senegal, this study aimed to investigate childhood vaccination coverage and its determinants according to the mothers' presentation of vaccination cards, as well as the determinants of such presentation.

Data collection started in April 2017 and ended that December. From the DHS data, this analysis was restricted to children aged 12-5 months (n= 4,032), and it assessed vaccination coverage and associated sociodemographic factors with weighted multivariate logistic regressions. Stratified multivariate logistic regressions were also performed to investigate factors associated with routine childhood immunisation uptake of the Bacillus Calmette-Guérin (BCG) vaccine, recommended for administration shortly after birth, as well as of the vaccines against yellow fever and measles (recommended at 9 months).

In short, vaccination coverage estimates were significantly higher among children whose mothers showed the vaccination card to the interviewer than for those whose mothers did not. Comparison of vaccination coverage estimates according to the vaccination card or parental recall resulted in a 5-10% difference in estimated coverage for the BCG, pentavalent, measles, and yellow fever vaccines, but a huge difference for the polio vaccine (93.0% with the card, 32.0% without it). As a result, the difference was also huge for complete immunisation (81.7% with vs 28.3% without the card).

In the multivariate analyses, most of the factors related to either children's or mothers' characteristics had no statistically significant effect on the presentation of the vaccination card, except for the child's age and mother's media exposure (e.g., mothers who never watched TV, listened to the radio, or read newspapers were less likely to have a vaccination card). The researchers explain that these media consumption patters are also indicators of exposure to prevention campaigns that promote vaccination and may thus be considered a supply-side effect.

Another significant factor was related to mothers' attendance at health facilities: Mothers who had attended antenatal care (ANC) were more likely to present the vaccination card (adjusted odds ratio (aOR) = 2.23), while those who gave birth at home (instead of at a health facility) were less likely to do so (aOR = 0.75). This finding leads the researchers to hypothesise that the card serves as a concrete manifestation of a bond between mothers and the healthcare system.

As the paper elaborates, "the patterns of vaccination determinants depended on which vaccine was considered, which is consistent with contemporary vaccine hesitancy."

Reflecting on the overall findings, the researchers note that the fact that estimated immunisation coverage rates were lower in the "no card" subsample is consistent with previous studies that have found mothers' ability to present this card to be a strong predictor of complete childhood immunisation. In looking at the significant gap related to polio case, they note that, contrary to most other childhood vaccines used in Senegal, which are injected, the polio vaccine is taken orally as drops. Previous studies have shown that laypeople frequently confuse injection with vaccination, since they tend to consider that vaccination always involves an injection. This might explain at least in part the considerable discrepancies observed between maternal recall and data from vaccination cards. "As a result, parents' misunderstanding of polio vaccine leads not only to underestimated vaccination coverage among children whose mothers were not able to present their vaccination card to interviewers but also to a massive mechanical underestimation of complete immunization coverage."

The researchers conclude that, "when there was a bond between the family and the health system, embodied by the ability to present the vaccination card, vaccinations were mainly driven by demand-side effects that illustrated the social differentiation of vaccination-related behaviors. Conversely, in the absence of such a bond, vaccinations tended to be mainly driven by supply-side effects. According to the theoretical framework proposed by the WHO [World Health Organization] to understand contemporary vaccine hesitancy..., this hesitancy is a matter of complacency, convenience, and confidence."