Big Catch-up vaccination initiative in Central and West Africa: progress, challenges and perspectives- a secondary analysis of aggregated program data.

Abstract

Introduction: WHO and other partners initiated Big Catch-up (BCU) to catch up children aged 12 to 59 months (about 5 years) who have never been vaccinated or are under-vaccinated because of the COVID-19 pandemic. Among the eligible countries are 16 from Central and West Africa. This study aims to analyze challenges and opportunities for this global initiative's success.

Methods: this was a secondary analysis of aggregated program data conducted in 16 countries in Central and West Africa eligible for the BCU. Data were collected through the BCU plans developed by countries, on vaccination coverage for each antigen included, epidemiological surveillance data for vaccine-preventable diseases (VPD) in countries and narrative reports on the implementation of BCU. The proportions of remaining targets to be achieved by country are obtained by dividing the number of children vaccinated in the numerator by the targets for zero doses or under-immunized children in the denominator by antigen. A simple logistic regression was performed to establish relationships between vaccination and the occurrence of vaccine-preventable diseases after COVID-19 and the implementation of BCU.

Results: outbreaks of VPD increase significantly in post-COVID-19 cases and during BCU implementation. All countries except Nigeria still have at least 70% of targets to catch up by December 2025. Two countries are categorized as making good progress, having achieved more than 50% vaccination coverage and DTP and measles: Nigeria and Mali. Cameroon, Côte d'Ivoire and Burkina Faso are making average progress in terms of vaccination coverage of the same antigens between 20-49%.

Conclusion: this initiative helped to curb the occurrence of VPD epidemics. However, the challenges are enormous. Countries must continue to organize further large-scale catch-up rounds and seize every opportunity for vaccination to significantly reduce ZD and Ui and thus VPD epidemics.