CD4 and respiratory syncytial virus bronchiolitis: Granzymes are proteinases that are expressed by various immune cells including T cells.39, 40 Children with severe RSV bronchiolitis have increased the production of granzymes from immune cells,41 and Tregs help control lung inflammation during RSV infection in a GZB‐dependent manner.42 However, after adjusting with covariates, we did not find a significant difference in the percentage of GZB+CD4+T cells after in vitro stimulation of CD4+ T cells between the recurrent wheezing group and those who never wheezed.