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Prevalence of Human Papillomavirus and Estimation of Human Papillomavirus Vaccine Effectiveness in Thimphu, Bhutan, in 2011–2012 and 2018

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.


PRIMARY FUNDING SOURCE
Bill & Melinda Gates Foundation.