The effect of vitamin A supplementation administered with missing vaccines during national immunization days in Guinea-Bissau

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Abstract
Background WHO recommends high-dose Vitamin A supplementation (VAS) at vaccination contacts after 6 months of age. It has not been studied whether the effect of VAS on mortality depends on the type of vaccine. We have hypothesized that VAS administered with measles vaccine (MV) is more beneficial than VAS with diphtheria–tetanus–pertussis (DTP) vaccine. We assessed the effect of VAS administered with different vaccines during national immunization days (NIDs). Methods In 2003, VAS was distributed during NIDs in Guinea-Bissau. Children 6 months or older were given VAS, and if they were missing vaccines, these were often given as well. We compared survival between children who had received VAS alone, VAS with DTP or DTP + MV, or VAS with MV. We also compared the survival between participants and non-participants. We followed 6- to 17-month old children until 18 months of age and analysed survival in Cox models. Results Twenty of 982 VAS-recipients died during follow-up. The mortality rate ratio (MRR) for VAS with DTP + MV or VAS with DTP was 3.43 (1.36–8.61) compared with VAS only. There were no deaths among those who received VAS with MV alone (P = 0.0005 for homogeneity of VAS effects). Children who received VAS with DTP had higher mortality than non-participants who did not receive VAS [MRR = 3.04 (1.31–7.07)]. Conclusion The study design does not allow for definite conclusions. However, the results are compatible with our a priori hypothesis that VAS is more beneficial when given with MV and potentially harmful when given with DTP. Randomized trials testing the impact on mortality of the current WHO policy seem warranted.