BACKGROUND

Understanding human papillomavirus (HPV) transmission dynamics within couples is necessary for optimal vaccine catch-up strategies. We used data from the Transmission Reduction and Prevention with HPV Vaccination (TRAP-HPV) study to estimate sex-specific incidence and transmission rates.

METHODS

The TRAP-HPV study enrolled (2014-2022) new (≤6 months) heterosexual couples aged 18+ in Montreal, Canada. The study employed a 2 × 2 factorial design. Participants (n = 308) were randomized into four groups: neither partner vaccinated against HPV, only the male partner vaccinated against HPV, only the female partner vaccinated against HPV, or both partners vaccinated against HPV. Genital samples, collected at 0, 2, 4, 6, 9, and 12 months, were genotyped for 36 HPV types. We performed time-to-event analyses for vaccine-targeted HPVs (6/11/16/18/31/33/45/52/58) and HPVs phylogenetically related (35/39/44/59/67/68/70) and unrelated (26/34/40/42/51/53/54/56/61/62/66/69/71/72/73/81/82/83/84/89) to vaccine-targeted types, using type-specific HPV infections as the unit of analysis.

RESULTS

Participants had a mean age of 25.5 years (SD 6.0), and a median of 6 (IQR: 2-15) lifetime sexual partners. Among males, incidence rates (in events/1000 months) were 0.99 (95 % CI: 0.17-3.07) and 1.67 (95 % CI: 0.75-3.51) in the two groups with vaccinated males versus 2.42 (95 % CI: 0.97-7.63) and 3.35 (95 % CI: 1.95-6.30) in the groups with unvaccinated males. Results were similar for the three HPV groups.

CONCLUSIONS

There was no consistent pattern of protection against incident HPV detection in females and no indication that recent vaccination was associated with lower transmission in discordant couples or with protection for one's partner. Findings should not be generalized to younger populations.