Environmental disasters have increased in frequency and intensity as a result of climate change.Can timely intervention help protect against the health impacts of these disasters? We study this question by leveraging data from a double-blind cluster-randomized controlled trial of at-birth vitamin A supplementation, which boosts immune system functioning, in Bangladesh. During the trial, a large tornado swept through the study area, affecting both treatment and control clusters. Tornado exposure in utero and in infancy decreased birth size and physical growth,and increased the incidence of severe fevers. But infants who received supplementation were protected from these negative effects.