Introduction No previous studies have measured HPV seroconversion rates following incident HPV infections of the anus. We examined these in teenage men who have sex with men (MSM).

Methods A cohort of 200 MSM aged 16–20 years were assessed at baseline, 3, 6 and 12 months. At each visit penile and anal swabs were collected for HPV DNA and serum for HPV antibodies for types 6, 11, 16 and 18. Seroconversion was defined as the detection of HPV antibodies following a negative antibody result for the same HPV genotype at baseline.

Results The seroincidence rates for HPV types 6, 11, 16 and 18 were: 18.8, 6.7, 3.9, and 5.8 per 100 person-years respectively. Men who experienced incident anal HPV infections from types 6 or 11 were significantly more likely to develop serum antibodies to the same HPV type than those who experienced incident anal infections from types 16 and 18 (72.7% vs 18.2%, Odds ratio (OR) = 12.0, 95% Confidence interval (CI): 2.5–58.1). However the likelihood to seroconvert did not differ between men who experienced incident penile HPV infections from types 6 or 11 and those who experienced incident penile infections from types 16 or 18 (42.9% vs 20.0%, OR = 3.0, 95% CI: 0.2–53.2). The median time between incident anal HPV infection and seroconversion for HPV 6, 11, 16, and 18 was: 91 days, 38 days, 161 days and 182 days respectively.

Conclusion Serum antibody responses were more likely to occur following anal infections with HPV types 6 and 11 than with types 16 and 18. Seroconversion may occur at a variable number of months after anal HPV infection.

Disclosure of interest statement This investigator initiated study was funded by Merck. Merck had no input into the design, analysis or reporting of the study. CKF has received honoraria from CSL Biotherapies and Merck and research funding from CSL Biotherapies. CKF owns shares in CSL Biotherapies the manufacturer for Gardasil. JSH has received an honorarium from CSL Biotherapies and is an investigator on an Australian Research Council funded project (LP0883831) that includes CSL Biotherapies as a research partner. AEG has received honoraria and untied research funding from CSL biotherapies, and has received honoraria from Merck. SMG has received advisory board fees and grant support from CSL and GlaxoSmithKline, and lecture fees from Merck, GSK and Sanofi Pasteur; in addition, she has received funding through her institution to conduct HPV vaccine studies for MSD and GSK. SMG is a member of the Merck Global Advisory Board as well as the Merck Scientific Advisory Committee for HPV. None of this relates to this specific work. MYC reported his institution received a grant from Merck Sharp Dohme that supported the conduct of the study. MGL receives grants from Bristol Myer Squibb, Gilead, GlaxoSmithKline, Janssen-Cilag, Merck, Pfizer and Roche which are not related to this project. All other authors have no conflicts of interest.