Assessing Vaccine Coverage and Timeliness in Bamako, Mali after the Introduction of Rotavirus Vaccine: A Modified Immunization Cluster Survey

Abstract

Vaccine coverage and timeliness are critical metrics for evaluating the performance of immunization programs. Following the introduction of rotavirus vaccine in Bamako, Mali, we conducted two cluster surveys spaced approximately 1 year apart to evaluate these metrics among children 9 to 20 months of age. Using the child's immunization card or the medical record at the center of administration, each selected child's immunization status was determined at 9 and 12 months of age. Deviations from the WHO-recommended immunization schedule were described by the median delay and fraction of children receiving doses outside of recommended age ranges. Overall, 1,002 children were enrolled in the two surveys combined; 80.1% of children born 7 to 12 months after introduction (survey 1) received three doses of pentavalent rotavirus vaccine (ROTA3) by 9 months of age, which increased to 86.1% among children born 17 to 26 months after introduction (survey 2). Concomitantly, coverage with the third dose of diphtheria-pertussis-tetanus-containing vaccine (DPT3) by age 9 months was 86.5% (survey 1) and 88.9% (survey 2); by age 12 months, 61.3% and 72.4% of children, respectively, had received all scheduled immunizations. The median delay in ROTA3 and DPT3 administration were similar at about 3.4 weeks. Within 3 years of introduction, coverage of rotavirus vaccine among Bamako infants achieved coverage similar to DPT3 and is approaching the Global Vaccine Action Plan goal of 90% coverage by 2020. However, timeliness of coverage remains a concern.

Figure 1.

Example map used for identifying survey clusters. Clusters were identified and drawn on maps of the Bamako communes (A, commune 1 shown here). Each cluster was divided into a grid of 20 cells (B).

Figure 2.

Consort diagram of enrollment in 2016 and 2017 surveys and contribution to overall analysis.

Figure 3.

Age of diphtheria, pertussis, tetanus-containing vaccine (DPT), rotavirus, measles, and yellow fever vaccine administration in Bamako, Mali. Doses of DPT and rotavirus vaccine are scheduled to be administered at 6, 10, and 14 weeks. Measles and yellow fever are scheduled to be administered at 9 months of age and overlapped perfectly in our data. This figure appears in color at www.ajtmh.org.