How health technology interacts with underlying cultural norms may have unanticipated consequences for development. Recent policy debates on closing the gender gap in developing countries have focused on affirmative action and economic growth, but there are reasons to expect that policies targeting the health of young children might also be effective. I investigate a national vaccination campaign targeting under-fi…ve children in Turkey, and document gains in human capital among age-eligible children of both sexes but spillover effects that accrue exclusively to older girl siblings. These …findings are consistent with predictions from a standard intrahousehold model of time allocation in the presence of gender norms regarding the division of household labor and suggest technologies and policies that improve the health of young children may have the added benefi…t of improving educational outcomes for their older sisters.