The challenge of achieving immunity through multiple-dose vaccines in Madagascar
Résumé
Many childhood vaccines require multiple doses be delivered within a narrow time window to provide adequate protection and reduce disease transmission. Accurately quantifying vaccination coverage is complicated by limited individual-level data and multiple vaccination mechanisms (routine and supplementary vaccination programs). We analyzed 12,541 vaccination cards from six districts across Madagascar for children born in 2015 and 2016. For three vaccines – pentavalent diphtheria-tetanus-pertussis-HepB-Hib vaccine (DTP, 3 doses), pneumococcal conjugate vaccine (PCV10, 3 doses) and rotavirus vaccine (2 doses), we used the dates of vaccination and birth to estimate coverage at one-year of age and timeliness of delivery. Vaccination coverage at one-year of age for the first dose was consistently high with decreases for subsequent doses: DTP (91%, 81%, 72%), PCV10 (82%, 74%, 64%) and rotavirus (73%, 63%). Coverage between urban districts and their rural counterparts did not differ consistently. For each dose of DTP, the overall percentage of individuals receiving late doses was 29%, 7%, and 6%; estimates were similar for other vaccines. Vaccination weeks, designed to catch-up children who had missed routine care, did not appear to increase the likelihood of being vaccinated. Maintaining population-level immunity with multiple-dose vaccines requires a robust standalone routine immunization program.
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