Reduction in Short-term Outpatient Consultations After a Campaign With Measles Vaccine in Children Aged 9–59 Months: Substudy Within a Cluster-Randomized Trial

Background We assessed a measles vaccination campaign’s potential short-term adverse events. Methods In a cluster-randomized trial assessing a measles vaccination campaign’s effect on all-cause mortality and hospital admission among children aged 9–59 months in Guinea-Bissau, children received a measles vaccination (intervention) or a health check-up (control). One month to 2 months later, we visited a subgroup of children to ask mothers/guardians about outpatient consultations since enrollment. In log-binomial models, we estimated the relative risk (RR) of nonaccidental outpatient consultations. Results Among 8319 children (4437 intervention/3882 control), 652 nonaccidental outpatient consultations occurred (322 intervention/330 control). The measles vaccination campaign tended to reduce nonaccidental outpatient consultations by 16% (RR, 0.84 [95% confidence interval {CI}, .65–1.11]), especially if caused by respiratory symptoms (RR, 0.68 [95% CI, .42–1.11]). The reduction tended to be larger in children who prior to trial enrollment had a pentavalent vaccination (diphtheria, tetanus, pertussis, hepatitis B, and Haemophilus influenzae type b) as the most recent vaccination (RR, 0.61 [95% CI, .42–.89]) than in children who prior to trial enrollment had a routine measles vaccination as the most recent vaccination (RR, 0.93 [95% CI, .68–1.26]) (P = .04 for interaction). Conclusions In the short term, a measles vaccination campaign seems not to increase nonaccidental outpatient consultations but may reduce them. Clinical Trials Registration NCT03460002.