Evidence for Protective Immunity to Chlamydia Trachomatis Genital Infection

Protective immunity to an infection may be complete (no detectable infection after re-exposure) or partial (shorter duration of organism shedding and/or lower organism burden after re-exposure). Definitive human studies are not available, but cross-sectional studies show chlamydia prevalence, organism load and concordance rates in couples decrease with age, and organism load is lower in those with repeat infections. These data support the concept of some degree of protective immunity; however, protection appears partial at best and can be overcome upon re-exposure. Future studies of protective immunity will require longitudinal follow-up, frequent sampling, and special cohorts to help control for exposure.