Protection conferred by neonatal rotavirus infection against subsequent rotavirus diarrhea.

A cohort of newborns in New Delhi who were nosocomially infected with rotavirus during their first days of life were followed twice weekly for 14-23 months to determine whether neonatal infection protected them against subsequent episodes of rotavirus diarrhea. Infection occurred in 60% by the fourth day of life, was asymptomatic, and was caused predominantly by an unusual rotavirus strain (G9 P11) not previously identified in humans. The 148 children with neonatal rotavirus infection had 46% fewer attacks of rotavirus diarrhea in the follow-up period than the 56 infants without nosocomial infection (0.23 vs. 0.42 episodes/child-year, P < .05). This protection was concentrated among infants in their first year of life and was not associated with a significant decrease in disease severity. Consideration of this strain as a vaccine candidate will require further assessment of its natural protection under field conditions.