Evaluating potential associations between prior maternal yellow fever vaccination and protection against infant adverse outcomes following Zika virus antenatal exposure

Differences in maternal YF NAb titers by ZIKV exposure and microcephaly suggest a potential protective effect of YF vaccination against ZIKV acquisition and/or development of microcephaly, which should be investigated. Developmental delay, although not associated with maternal YF immunity, was associated with antenatal ZIKV exposure, less prenatal care visits, and being small for gestational age.