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Table 4 RECAMP-OPV - potential effect modifiers

From: Research protocol of two concurrent cluster-randomized trials: Real-life Effect of a CAMPaign with Measles Vaccination (RECAMP-MV) and Real-life Effect of a CAMPaign with Oral Polio Vaccination (RECAMP-OPV) on mortality and morbidity among children in rural Guinea-Bissau

Effect modifiersRationale
SexPrevious studies have demonstrated that the effect of OPV is stronger in boys than girls [4, 15, 47].
One vs two doses (2nd dose 1 month after enrolment)Observational studies indicate that additional doses of OPV offer additional benefits [15].
Age at first dose of OPVA prior study has indicated that the effect of subsequent vaccines may vary with the age at which the gut was primed [16].
Season of enrolmentSome interventions (eg MV and Vitamin A) have stronger effects when given in the dry season [29, 48]. We will investigate whether the effect of OPV varies for children enrolled in the dry season (December–May) versus children enrolled in the rainy season (June–November)
Vitamin A supplementsVitamin A supplementation may amplify the NSEs of vaccines [49, 50]. We will examine whether the effect of OPV vary before and after being eligible for vitamin A supplementation after enrolment
Prior OPV campaignRepeated doses of OPV offer additional benefits [15]. If OPV campaigns take place during the study, we will assess whether the effect is similar in children having been exposed/not exposed to prior OPV campaigns.