The mortality effects of disregarding the strategy to save doses of measles vaccine: a cluster-randomised trial in Guinea-Bissau

Abstract

IntroductionMeasles vaccine (MV) may improve health beyond measles protection. To avoid wastage from multi-dose vials, children in Guinea-Bissau are only measles vaccinated when aged 9–11 months and when six or more children are present. We assessed health impacts of providing MV to all measles-unvaccinated children 9–35 months.MethodsWe cluster-randomised 182 village clusters under demographic surveillance in rural Guinea-Bissau to an ‘MV-for-all-policy’ arm where we offered MV regardless of age and number of children present at our bi-annual village visits, or a ‘Restrictive-MV-policy’ arm where we followed national policy. Measles-unvaccinated children aged 9–35 months were eligible for enrolment and followed to 5 years of age. In intention-to-treat analyses, we compared mortality using Cox regression analyses with age as underlying timescale. The primary analysis was for children aged 12–35 months at eligibility assessment. Interactions with several background factors were explored.ResultsBetween 2011 and 2016, we followed 2778 children in the primary analysis. MV coverage by 3 years was 97% among children eligible for enrolment under the MV-for-all-policy, and 48% under the Restrictive-MV-policy. Mortality was 59% lower than anticipated and did not differ by trial arm (MV-for-all-policy: 45/1405: Restrictive-MV-policy: 44/1373; HR: 0.95 (95% CI 0.64 to 1.43)). The effect of MV-for-all changed over time: The HR was 0.53 (95% CI 0.27 to 1.07) during the first 1½ years of enrolment but 1.47 (95% CI 0.87 to 2.50) later (p=0.02, test of interaction). Explorative analyses indicated that the temporal change may be related to interactions with other childhood interventions.ConclusionThe MV-for-all-policy increased MV coverage but had no overall effect on overall mortality.Trial registration numberNCT01306006.