HBoV infection has been shown (by PCR of NPA samples) to be most prevalent in children 6 months to 3 years of age; adults are less affected (8, (24) (25) (26) (27) (28) (29) (30) . Consistent with this finding, the incidence of serologically verified acute HBoV infections in our study was highest (28%) during the second year of life; median age of children with acute HBoV infections was 1.3 years. Only 2 children were infected at >4 years of age; 1 of them was seronegative. Children <6 months of age might be protected from infection by maternal antibodies. Rapidly decreasing seroprevalence rates from ≈90% in infants <3 months of age to ≈5% in infants 6 months of age were reported (12, 13) . In our study, 26% of 27 children <6 months of age (including 1 infant <3 months of age) had maternal antibodies, and only 1 child in this age group had an acute HBoV infection.