Age-related changes in the prevalence of precipitating antibodies to BK virus in infants and children.

Nearly 1000 sera from children were tested by immunoelectro-osmophoresis against BK virus, and age-specific prevalence rates were estimated from birth until the age of 12 years. Declining rates during the first 12 months showed the waning of passive immunity, which at birth reflects the mother's immune status. The changes of prevalence suggested that the peak incidence of primary infections occurred at about 2 years, with an estimated peak annual rate of 24.6%.