Causal Direction Between Respiratory Syncytial Virus Bronchiolitis and Asthma Studied in Monozygotic Twins

We found no differential effect from severity of RSV infection on the development of asthma and allergy in MZ twin pairs discordant for RSV hospitalization in infancy. This argues against a specific effect of severe RSV infection in the development of asthma and allergy. Because of the small sample size, this study must be considered as a hypothesis-generating study.