The goal of a recent study published in the BMJ Clinical Research was to determine the association between exposure to 2009 pandemic H1N1 (pH1N1) influenza vaccination during pregnancy and negative health outcomes during early childhood. This was a retrospective cohort study, wherein population-based birth registry linked with health administrative databases were searched in the province of Ontario, Canada. All live births from November 2009 through October 2010 (n=104 249) were included, and children were followed until the age of 5 years, to ascertain study outcomes. Rates of immune related – infectious diseases, asthma; non-immune related – neoplasms, sensory disorders; and non-specific morbidity outcomes – urgent or inpatient health services use, pediatric complex chronic conditions, were evaluated from birth to 5 years and under-5, childhood mortality was also assessed. The results revealed that of 104,249 live births, 30% were exposed to pH1N1 influenza vaccination, in-utero. However, no significant associations were found with upper or lower respiratory infections, otitis media, any infectious diseases, neoplasms, sensory disorders, urgent and inpatient health services use, pediatric complex chronic conditions or mortality. A weak association was observed between prenatal pH1N1 vaccination and increased risk of asthma and decreased rates of gastrointestinal infections. These results remained unchanged in sensitivity analyses accounting for any potential differential healthcare seeking behavior or access between exposure groups. Thus, no associations were noted between exposure to pH1N1 influenza vaccine during pregnancy and most five-year pediatric health outcomes.