Overall effect of a campaign with measles vaccine on the composite outcome mortality or hospital admission: A cluster-randomized trial among children aged 9-59 months in rural Guinea-Bissau

OBJECTIVES: Campaigns with measles vaccine (C-MV) are conducted to eradicate measles, but prior studies indicate that MV reduces non-measles mortality and hospital admissions too. We hypothesized that C-MV reduces death/hospital admission by 30%.

METHODS: Between 2016-2019, we conducted a non-blinded cluster-randomized trial randomizing village clusters in rural Guinea-Bissau to a C-MV targeting children aged 9-59 months. In Cox proportional hazards models, we assessed the effect of C-MV, obtaining hazard ratios (HR) for the composite outcome (death/hospital admission). We also examined potential effect modifiers.

RESULTS: Among 18,411 children (9636 in 111 intervention clusters/8775 in 110 control clusters), 379 events occurred (208 intervention/171 control) during a median follow-up period of 22 months. C-MV did not reduce the composite outcome (HR 1.12, 95% confidence interval 0.88-1.41). Mortality among enrolled children (5.3 intervention and 4.6 control, per 1000 person-years) was approximately half the pre-trial mortality rate (11.1 intervention and 8.9 control, per 1000 person-years). Neither planned nor explorative analyses of potential effect modifiers explained the contrasting results to prior studies.

CONCLUSION: C-MV did not reduce overall mortality or hospital admission. This might be explained by changes in disease patterns, baseline differences in health status, and/or modifying effects of other campaigns during follow-up.