Prevalence of Chlamydial antibodies in children.

Humoral antibody to Chlamydia trachomatis was determined in 820 infants and children. Of 120 newborns, 63 (52.5%) had indirect immunofluorescence titers of 1:8 or more to C trachomatis (L-2 strain) in the cord blood. Among the 700 infants and children, a progressive increase in seropositivity was observed: 5% for 1- to 2-years-olds, 25% for 3- to 6-year-olds, and 43% for 7- to 15-year-olds. Seropositivity rates were not related to sex or race; however, significantly higher titers were observed in female compared with male subjects and in blacks compared with whites. These data suggest that C trachomatis infection occurs commonly in children. The nature of the illness, if any, preceding seroconversion is unknown and needs to be elucidated.