This study reports the persistence and clearance of oral HPV infections among a longitudinal cohort of men from three countries. Oral HPV infections detected as prevalent, with an unknown infection history, were less likely to clear compared to infections newly acquired during the study follow-up, confirming they should be investigated separately. Among prevalent infections, older age and increased frequency of oral sex were significantly associated with lower likelihood of clearing an infection and timepoint persistenct of ≥6- and ≥12-months. Among incident infections, men with a larger number of lifetime female partners were less likely to clear their infection (aHR: 0.74; 95% CI: 0.53–1.04) though this did not reach statistical significance. Men reporting other race, non-Hispanics, current smokers, and men reporting a larger number of male or female sexual partners had increased risk of an incident infection persisting ≥6 months. Similar results were observed for factors associated with persistence of oral HPV 16 infection.

We separately investigated and observed differences in probability of clearance of an oncogenic oral HPV infection among incident and prevalent infections (median duration of 0 and 6 months, respectively; and 20 and 24 months, respectively among men who persisted 6 months or more). In the same HIM Study cohort, 6–8 months for genital HPV infections was observed and decreasing with increasing age¹⁰. At the anus, a median duration of 6–9 months after an incident infection and 13–27 months after a prevalent infection was observed¹¹. D’Souza and colleagues recently reported a median oncogenic oral HPV duration of 14 months combining incident and prevalent infections, using the same definition for clearance as our study (i.e. two consecutive negative HPV tests) among people living with or at risk of HIV¹². Similar to our study, they also observed lower liklihood of clearance among prevalent infections and among older participants¹². We observed non-conclusive patterns in oral oncogenic HPV infection clearance by age. Among all incident infections, duration was not different by age, but was marginally different by age among men whose infections persisted at least 6 months. Among prevalent infections, duration was marginally different by age only when transient infections were included in analyses. However when modeled for an association with clearance, age was significantly, independently associated, a result that supports oral HPV surveillance at older ages when prevalent, long-lasting (>2years) infections may be of concern. Our results indicate age may be an important factor for oral HPV persistence, but the evidence is inconclusive given differences observed with incident vs. prevalent infections. As little is known regarding the timing of oral HPV acquisition^10,11,12 definitive statements regarding age associations with lower rates of prevalent detected oncogenic oral HPV infections is not possible. However, our recent publication investigating oral HPV acquisition reported no difference in the rate of oral HPV acquisition across age groups⁹. With older age there is likely a decrease in immune function which may reduce ability to clear an oral HPV infection. In fact, D’Souza et al., also observed that people living with HIV, a known immunocompromised population, are less likely to clear an oral HPV infection¹².

Overall, higher levels of sexual activity was a key factor associated with lower likelihood of oral oncogenic HPV clearance across both infections types. This was pronounced when persistence was assessed at key timepoints (≥6- and ≥12-month persistence) for both infection types. While previous studies both in The HIM Study^9,13 as well as other cohorts^14,15 have found similarly significant associations with oral HPV acquisition it is unclear how increased exposure via sexual acitivity may lead to a reduced ability to clear the infection and, in fact, may represent a repeated exposure to virus. Low seroconversion rates following an HPV infection¹⁶ occur in men and high risk of recurrence has been observed with genital HPV infections¹⁷, indicating a potential pathway between sexual activity and oral HPV persistence.

Unexpectedly, smoking was not associated with clearance of oral HPV. Although, among incident infections, smoking was significantly associated with persistence of ≥6-months, but not ≥12-months suggesting smoking may have an impact on short-term persistence. This is unlike results from studies of HPV at other anatomic sites¹⁸ including those from HIM Study investigations of genital HPV acquisition¹⁹ and persistence²⁰. Smoking has been hypothesized to increase risk of acquisition and reduce clearance of oral HPV infections due to its’ ability to reduce immune function and specifically T cell function^21,22, which is necessary to clear an HPV infection²³. Last, our study observed an increased risk of ≥6- and ≥12-month persistence for White men and men reporting Other race, compared to Black men, similar to an Australian study²⁴, but race was not associated with overall likelihood of clearance in Cox models. Of note, the patterns observed in our study for smoking and race are similar to the associations of these variables with HPV-OPC risk^25,26. Other considerations, such as host immune function, HPV recurrence and/or latency, and duration from infection to HPV-OPC, neeed to be explored to fully understand natural history and progression to cancer.

A recent study concluded little benefit of vaccination in men beyond 26 years of age²⁷ after simulated data observed 70% of oral HPV16 infections occurred by age 26. However, this was modeled on cross-sectional US prevalence studies rather than prospective cohorts.The findings of the current study surrounding older age warrants further consideration. Coupled with similar results from D’Souza et al., there may be a rationale for vaccination through age 45 to prevent oral HPV infections more likely to persist. This is further supported by our recent prospective study which concluded equal risk of oral HPV acquisition across the lifespan after observing no difference in acquisition of oral oncogenic HPV across age groups⁹.

While our study has several strengths due to the prospective cohort study design and long-term follow-up of over 3000 men, there are limitations to note. This was a comprehensive investigation of factors associated with oral HPV persistence and as such only a few self-reported factors representative of each risk category assessed at baseline (i.e. demographics, substance use, sexual behavioral, and oral health) were included in the models. With self-report there is an inherent risk of reporting and recall bias. To minimize bias, surveys were self-administered via computer in a private room and the same questions asked throughout follow-up. The oral gargles are collected every 6 months, thus the precise date of infection acquisition and clearance are unknown—a common limitation of longitudinal cohort studies. The methods for defining clearance of an oral HPV infection used in this study are consistent with those of others studies^12,28. The specimen used to detect oral HPV DNA, the oral gargle, does not specifically target the oropharynx; prior studies have shown performance to be lower than measuring HPV directly in the tumor²⁹. At this time, the oral gargle is the current standard for detection of oral HPV in cancer free popualtions. Further, the SPF₁₀ PCR-DEIA-LIPA₂₅ assay, a sensitive and robust test for HPV genotyping, was utilized on all oral specimens in the same laboratory.

This study evaluates the clearance and investigate the factors associated with clearance of an oral oncogenic HPV infection in a prospective study of healthy men from the US, Brazil, and Mexico. With follow-up of up to 8 years and oral HPV testing at six month intervals, it represents one of the largest and most comprehensive evaluations of oral HPV natural history to date. We observed differences in clearance and risk factors for incident versus prevalent infections which is an important consideration as more studies investigate and draw conclusions on oral HPV natural history. We found no factors to be significantly associated with the ability to clear a newly acquired infection. Whereas among prevalent infections, older age and more oral sex was independently significantly associated with clearance. Further study is clearly needed to disentangle host demographic and behavioral factors, as well as immune response and viral factors at play with oral HPV persistence to address the increasing incidence of HPV-related OPC in men.