Prevalence of Human Papillomavirus and Estimation of Human Papillomavirus Vaccine Effectiveness in Thimphu, Bhutan, in 2011-2012 and 2018 A Cross-sectional Study

Abstract

Background: Bhutan implemented a national program for human papillomavirus (HPV) vaccination in 2010 involving girls aged 12 to 18 years and achieving nearly 90% coverage. Objective: To estimate HPV vaccine effectiveness in a city in Bhutan. Design: 2 cross-sectional surveys, 2011-2012 and 2018. Setting: 2 hospitals in Thimphu, capital of Bhutan. Participants: Sexually active women aged 17 to 29 years: 1445 participants from the baseline survey and 1595 from the repeated survey. Intervention: National HPV vaccination program. Measurements: HPV was assessed in cervical cell samples by using general primer GP5+/GP6+-mediated polymerase chain reaction. Human papillomavirus types were stratified as vaccine types (HPV6/11/16/18) and nonvaccine types. Age- and sexual behavior-adjusted overall, total, and indirect (herd immunity) vaccine effectiveness (VE) was computed as (1 - HPV prevalence ratio) for HPV among all women and among unvaccinated women. Results: Between the 2 surveys, the prevalence of HPV vaccine types decreased from 8.3% to 1.4%, whereas the prevalence of nonvaccine types increased from 25.8% to 31.4%. The overall and indirect adjusted VE against vaccine-targeted HPV types was 88% (95% CI, 80% to 92%) and 78% (CI, 61% to 88%), respectively. Among women younger than 27 years, who were targeted by the vaccination program, the overall and indirect adjusted VE was 93% (CI, 87% to 97%) and 88% (CI, 69% to 95%), respectively. No impact on nonvaccine HPV types was detectable. Limitation: Hospital-based recruitment; self-reported vaccination status. Conclusion: In Bhutan, the prevalence of vaccine-targeted HPV types has decreased sharply, providing the first evidence of the effectiveness of a high-coverage national HPV vaccination program in a lower-middle-income country.