Natural history of oral HPV infection: Longitudinal analyses in prospective cohorts from Australia.

Oral infection with human papillomavirus (HPV) is likely to underpin the rapidly rising incidence of oropharyngeal squamous cell carcinoma; however, there are few data describing the natural history of oral HPV infection. We recruited 704 participants aged 20 to 70 years from worksites, universities and primary care practices in Brisbane, Australia. Participants completed questionnaires at baseline, 12 and 24 months and donate four saliva samples at baseline, 6, 12 and 24 months for HPV polymerase chain reaction testing and typing. We estimated the prevalence of oral HPV infection at baseline, incidence of new infections among those HPV-negative at baseline, clearance rate and persistent infections. At baseline, 10.7% of participants had oral HPV infections from 26 different HPV types. Sexual behaviours were associated with oral HPV infection, including more partners for passionate kissing (29 or more; odds ratio [OR] 3.4, 95% confidence interval [CI] 1.5-8.0), and giving and receiving oral sex (16 or more; OR 5.4, 95% CI 1.6-17.7 and OR 5.6, 95% CI 1.6-18.7, respectively). Of 343 participants, HPV-free at baseline and with subsequent saliva samples, 87 (25%) acquired new infections over the 24 months. Sixty-eight of 87 people included in the clearance analysis (78%) cleared their oral HPV infections. Clearance was associated with being a nonsmoker (OR 12.7, 95% CI 1.3-122.8), and no previous diagnosis of a sexually transmitted infection (OR 6.2, 95% CI 2.0-19.9). New oral infections with HPV in this sample were not rare. Although most infections were cleared, clearance was not universal suggesting a reservoir of infection exists that might predispose to oropharyngeal carcinogenesis.