Changes over time in the Chlamydia trachomatis serotype distribution in Finnish women

The distribution of Chlamydia trachomatis serotypes in the sexually active population may change over time. Serum from C. trachomatis seropositive women representing the 1980s, 1990s, and 2000s were available from a stratified random sample (11,067) of the Finnish Maternity Cohort for microimmunofluorescence-based classification. The C. trachomatis serotype distributions in the 1980s and 2000s were comparable, with serotypes G, E, and J being the most prevalent. In the 1990s the numbers of women seropositive for ≥ 2 serotypes peaked, and serotypes G/J were replaced by serotypes E/D. The temporary C. trachomatis serotype replacement parallels changes in the sexually active population in the 1990s in Finland.