Background: In spite of existing chlamydia screening and treatment programs in most developed countries, the high burden of chlamydia persists, especially among the youth (15-24-year-olds). Although there is currently no chlamydia vaccine, future development of an effective chlamydia vaccine is possible. In this study, we explore the potential cost-effectiveness of a hypothetical chlamydia vaccine for young females in the United States (US) and British Columbia (BC), Canada.
Methods: We constructed a simple heterosexual deterministic compartmental transmission model. Parameter values were obtained from the literature. The strategies we assessed included vaccination of 14-year-olds and catch-up vaccination for 15-24-year-old females in the context of an existing chlamydia screening program. For our base case, we assumed 30% annual screening coverage, 30% vaccine coverage, 75% vaccine efficacy, 10-year duration of vaccine-conferred immunity and $500 vaccine cost. We analyzed costs and benefits over a 50-year period and calculated the incremental cost-effectiveness ratio (ICER) of adding a chlamydia vaccination program to an existing chlamydia screening program. We also examine which model parameters had the most impact on the ICERs.
Results: In the base case, the estimated ICERs of vaccinating 14-year-olds were $32,244/QALY (US) and $14,829/QALY (BC) when compared to screening only. Extending the program by including catch-up vaccination for 15-24-year-olds (US) and 15-35-year-olds (BC) resulted in an estimated ICER of $48,564/QALY (US) and $24,074/QALY (BC). When we assumed a vaccine with perfect performance (i.e., 100% efficacy and lifelong duration of efficacy), the ICERs were reduced by more than half; vaccinating only 14-year-olds was cost-saving in the BC analyses. The estimated ICER was most sensitive to pre-vaccination chlamydia prevalence followed by the cost of vaccination, the duration of vaccine-conferred immunity and vaccine efficacy.
Conclusions: Our results suggest that an effective chlamydia vaccine could be cost-effective, particularly in high morbidity areas.