Non-specific effects of BCG vaccination on neutrophil and lymphocyte counts of healthy neonates from a developed country.

BCG vaccination is known to reduce neonatal mortality from infections in a pathogen-agnostic manner. In this observational study we report on whether an emergency granulopoietic response is elicited in term babies from a developed country following BCG vaccination. We studied a cohort of neonates re-admitted to the hospital from home for feeding support separated into 2 groups dependent on whether they had received BCG vaccination. Clinical data including gender, weight, gestational age, method of feeding and full blood count results were retrieved retrospectively. While lymphocyte counts increase following BCG vaccination irrespective of gender and in proportion with the time elapsed after vaccination, the increase in neutrophil counts, is only observed in boys. This increase appears to be temporary. Our results confirm the presence of emergency granulopoiesis following BCG vaccination in a neonatal cohort from a developed country. However, this effect appears to be gender-specific and is present only in boys.