Dr. Thea K. Fischer, of the University of Bergen, Norway, and colleagues prospectively followed 200 newborns in Guinea-Bissau for up to 2 years using weekly stool examination to detect rotavirus.

The incidence of rotavirus infection by ages 6 months, 1 year, and 2 years was 26%, 46%, and 74%, respectively. Diarrhea occurred in association with 17% of rotavirus infections in the first 3 months of life and with 60% of infections by 9 to 11 months of age. All rotavirus infections were asymptomatic after age 18 months.

Natural rotavirus infection conferred 52% protection against reinfection and 70% protection against rotavirus diarrhea, the team reports. "The protection estimates against reinfection within the same epidemic and in any subsequent epidemic were 66% and 34%, respectively," they add.

Dr. Fischer and colleagues conclude that the "high level of protection against symptomatic rotavirus infection provides an important incentive for development of a rotavirus vaccine."

J Infect Dis 2002;186:593-597.