In our paper1 we specifically explored the hypothesis linking autism spectrum disorder (ASD) to MMR vaccination. Our cohort is approximately 9 years from their MMR vaccination but our findings are identical to those of D’Souza et al2 whose subjects were 26–30 months from vaccination. Singh’s paper on measles antibody levels in autism compared with controls reports on a wide age range of children.3

Two correspondents refer to 735 “lost” children. This is a misunderstanding. As described in Baird et al,4 the original study design intended that only a subsample of those screened would be assessed in depth and these were selected at random within strata formed by …