Response to Comment on ‘Evaluating potential associations between prior maternal yellow fever vaccination and protection against infant adverse outcomes following Zika virus antenatal exposure’

We thank Drs Lin and Gang for their thoughtful comments and for highlighting the relevance of exploring how prior Yellow fever (YF) vaccination may modify susceptibility to Zika virus (ZIKV) infection and adverse infant outcomes [1]. Our study was not restricted to microcephaly. We examined whether yellow fever neutralizing antibody (YF NAb) titers were associated with protection against maternal ZIKV infection and, among ZIKV-exposed pregnancies, whether higher YF NAb titers were associated with a lower risk of early or late adverse infant outcomes. Regarding sample size, Tables 1 and 2 present descriptive clinical characteristics for all eligible mother–child dyads with available clinical data (n = 146), derived from the parent cohort [2] (n = 157) after exclusion of pregnancy losses. YF neutralization assays were performed only among mothers with available serum samples (n = 129), as stated in the “Methods” section [1]. Of these, nine mothers who were ZIKV-positive by plaque reduction neutralization test (PRNT) but had indeterminate timing of infection during pregnancy were excluded a priori from inferential analyses, resulting in a final analytical sample of 120 participants. We acknowledge that this distinction between descriptive and analytic denominators was insufficiently explicit in the tables and apologize for this oversight.