Vaccination of Young Women Decreases Human Papillomavirus Transmission in Heterosexual Couples: Findings from the HITCH Cohort Study

Background: Vaccination against human papillomaviruses (HPV) prevents HPV infections and, consequently, cervical lesions. However, the effect of vaccination on HPV transmission within couples is unknown. Methods: We used data from HITCH, a prospective cohort study of heterosexual couples (women ages 18-24 years) in Montreal, 2005 to 2013. Vaccination history was self-reported. Genital samples were tested for HPV DNA by PCR (linear array). Type-specific viral loads were quantified using real-time PCR. OR and HR were estimated using multilevel mixed-effects logistic regression and a parametric model for interval-censored survival-time data, respectively. Differences in viral loads were evaluated using the Friedman ANOVA test. Results: Among 497 couples, 12, 16, and 35 women received 1, 2, or 3 vaccination doses at baseline, respectively. Median age at vaccination was 18 years. Most women (92.1%) had their first coitus before vaccination. At baseline, partner concordance of persistent HPV6/11/16/18 infections was lower in vaccinated than unvaccinated women [adjusted OR = 0.10; 95% confidence interval (CI), 0.01-0.65] but not for non alpha 7/alpha 9/alpha 10-HPV types (adjusted OR = 1.00; 95% CI, 0.44-2.29). Incidence of persistent alpha 7/alpha 9/alpha 10 HPV types in women was inversely associated with vaccination status at baseline (adjusted HR = 0.12; 95% CI, 0.03-0.47). Likewise, male partners of vaccinated women had a lower incidence of alpha 7/alpha 9/alpha 10 HPV infections (adjusted OR = 0.22; 95% CI, 0.05-0.95). Vaccinated women with HPV 6/11/16/18 infections had lower viral loads (P = 0.001) relative to unvaccinated women. Conclusions: Vaccination of sexually active women significantly reduced transmission of alpha 7/alpha 9/alpha 10 HPV types in heterosexual couples. Impact: These results underscore and quantify the positive effect of HPV vaccination on HPV transmission within heterosexual couples.