Incidence of influenza virus infection in early infancy: a prospective study in South Asia.
ABSTRACT We evaluated infant sera from an immunization trial in Bangladesh to assess influenza hemagglutination inhibition antibody titer increases in 131 unimmunized infants from birth to 6 months. We detected 31 serologically defined infections. Combined with 10 additional rapid test-proven influenza cases, the minimal estimated incidence was 31 of 100 infants (95% CI: 24-41). These data suggest a high burden of influenza in young infants in tropical South Asia.