Figure 1.

Study design and flowchart according to the CONSORT guidelines. In the control group, before any OPV campaign, 1 death was in-hospital and is therefore only counted as a hospital admission for severe morbidity and 1 death was due to an accident, resulting in a combined nonaccidental severe morbidity count of 25 (1 death + 24 hospital admissions). After OPV campaigns in that group, 2 deaths were in-hospital and are only counted as hospital admissions for severe morbidity and 1 hospital admission was due to an accident, resulting in a combined nonaccidental severe morbidity count of 21 (1 death + 20 hospital admissions). ^aChildren that had received the meningococcal vaccine between MV1 and study enrollment at the national campaign in 2016 were excluded from the analyses as they had received a nonlive vaccine after their MV1. Abbreviations: HDSS, Health and Demographic Surveillance System; MV1, first measles vaccine; MV2, second measles vaccine; OPV, oral polio vaccine.