In Sub-Saharan Africa, one in eight children die before age 5. Sixty percent of these deaths are preventable by investments in child health as simple as immunizations, bed nets, or water puri?cation. This paper investigates how a household’s decision regarding such investment is a?ected by the size and gender composition of a child’s cohort. I focus on an important and previously ignored type of investment: non-rival goods that disproportionately bene?t child health, that is, club goods for kids. Employing data on childhood immunizations, I empirically estimate the response of club goods consumption to cohort characteristics. I present an innovative method to deal with the problem of endogenous fertility, common in cohort studies. Most rural Senegalese households are composed of multiple nuclear families, so that a child’s cohort is composed of both siblings and non-sibling children. Estimating within-household, I instrument cohort characteristics with those of the non-sibling (exogenous) portion. I ?nd that children with larger (or more male) cohorts of vaccine-eligible age are signi?cantly more likely to receive immunization. These ?ndings suggest that, at least with respect to club goods investment, children with larger cohorts may be better o?: a signi?cant ?nding for child health, as many illness prevention methods are of a club good nature.