With a borderline significance (P = 0.04), possibly because of our relatively small sample size, it remains to be concluded whether early natural exposure could also negatively influence vaccine seroconversion as previously observed in South Africa and Nicaragua [ 22 , 27 , 43 ].
Maternally acquired IgG did show a trend to affect seroconversion upon interquartile baseline titre comparisons consistent with other studies [ 22 ]; however, in our study this association did not reach statistical significance ( p = 0.06).
Based on our findings, we conclude that there is a clear trend in the seasonal peaks of breast milk IgA and corresponding troughs in infant serum IgA response to RV vaccination.