Longitudinal Study on Changes in COVID-19 Vaccination Intentions in Benin and Senegal: Insights from Generalized Estimating Equations (GEE)

Introduction

The COVID-19 pandemic led to strict measures and the rapid deployment of vaccines, which were adopted in Benin and Senegal. This longitudinal study employs Generalized Estimating Equations (GEE) to analyze the evolution of vaccination intent and its determinants. By examining attitudes, risk perceptions, and social influence, it provides insights into adherence dynamics and helps guide vaccination strategies in West Africa.

Methods

This is a longitudinal, descriptive, and analytical study. The sample includes 546 Beninese, and 319 Senegalese individuals aged 18 and above, selected using marginal quotas. Data collection was conducted through Random Digit Dialing (RDD) using a questionnaire based on the Theory of Planned Behavior (TPB) and the Health Belief Model (HBM). The influence of factors was assessed using a GEE model.

Results

The evolution of vaccination intent between the two data collection phases was more pronounced in Senegal (+12.5 points, p=0.000) than in Benin (+5.0 points, p=0.089). The increase was significant among women (+19.9 points, p=0.000) and individuals under 25 years old (+15.6 points, p=0.030), whereas in Benin, this younger group showed a decline (–11.5 points, p=0.009), with only those aged 25-59 years demonstrating an increase (+11.7 points, p=0.011). In both countries, individuals surveyed during the second phase had a significantly higher likelihood of expressing vaccination intent (Benin: OR = 6.9, p < 0.001; Senegal: OR = 5.0, p < 0.001).

Additionally, the increase in vaccination intent was influenced by common factors such as perceived benefits (Benin: OR = 1.191; Senegal: OR = 1.412), social influence (Benin: OR = 1.377; Senegal: OR = 1.310), and favorable attitudes toward vaccination (Benin: OR = 1.266; Senegal: OR = 1.254). However, differences emerged: in Benin, perceived efficacy (OR = 1.287) and behavioral control (OR = 1.203) were significant, whereas in Senegal, concerns about vaccine safety posed a greater barrier (OR = 0.685 compared to 0.781 in Benin).

Conclusion

This study highlights both common and specific determinants of vaccination intent in Benin and Senegal, particularly social influence and perceived vaccine benefits. However, contextual differences exist, such as the greater importance of perceived efficacy in Benin and the more pronounced impact of safety concerns in Senegal. These findings underscore the need to tailor communication strategies and strengthen public trust to improve vaccine uptake.