Detection of Incident Anal High-Risk Human Papillomavirus DNA in Men Who Have Sex With Men: Incidence or Reactivation?

Association of naturally acquired type-specific HPV antibodies and subsequent HPV re-detection: systematic review and meta-analysis

BACKGROUND

Understanding the role of naturally acquired (i.e., infection-induced) human papillomavirus (HPV) antibodies against reinfection is important given the high incidence of this sexually transmitted infection. However, the protective effect of naturally acquired antibodies in terms of the level of protection, duration, and differential effect by sex remains incompletely understood. We conducted a systematic review and a meta-analysis to (1) strengthen the evidence on the association between HPV antibodies acquired through past infection and subsequent type-specific HPV detection, (2) investigate the potential influence of type-specific HPV antibody levels, and (3) assess differential effects by HIV status.

METHODS

We searched Embase and Medline databases to identify studies which prospectively assessed the risk of type-specific HPV detection by baseline homologous HPV serostatus among unvaccinated individuals. Random-effect models were used to pool the measures of association of naturally acquired HPV antibodies against subsequent incident detection and persistent HPV positivity. Sources of heterogeneity for each type were assessed through subgroup analyses stratified by sex, anatomical site of infection, male sexual orientation, age group, and length of follow-up period. Evidence of a dose-response relationship of the association between levels of baseline HPV antibodies and type-specific HPV detection was assessed. Finally, we pooled estimates from publications reporting associations between HPV serostatus and type-specific HPV detection by baseline HIV status.

RESULTS

We identified 26 publications (16 independent studies, with 62,363 participants) reporting associations between baseline HPV serostatus and incident HPV detection, mainly for HPV-16 and HPV-18, the most detected HPV type. We found evidence of protective effects of baseline HPV seropositivity and subsequent detection of HPV DNA (0.70, 95% CI 0.61-0.80, NE = 11) and persistent HPV positivity (0.65, 95% CI 0.42-1.01, NE = 5) mainly for HPV-16 among females, but not among males, nor for HPV-18. Estimates from 8 studies suggested a negative dose-response relationship between HPV antibody level and subsequent detection among females. Finally, we did not observe any differential effect by baseline HIV status due to the limited number of studies available.

CONCLUSION

We did not find evidence that naturally acquired HPV antibodies protect against subsequent HPV positivity in males and provide only modest protection among females for HPV-16. One potential limitation to the interpretation of these findings is potential misclassification biases due to different causes.

Vaccine Effectiveness Against 12-Month Incident and Persistent Anal Human Papillomavirus Infection Among Gay, Bisexual, and Other Men Who Have Sex With Men

BACKGROUND

Real-world evidence of human papillomavirus (HPV) vaccine effectiveness (VE) against longitudinal outcomes is lacking among gay, bisexual, and other men who have sex with men (GBM). We compared 12-month incidence and persistence of anal HPV infection between vaccinated and unvaccinated GBM.

METHODS

We recruited GBM aged 16-30 years in Montreal, Toronto, and Vancouver, Canada, from 2017 to 2019. Participants were followed over a median of 12 months (interquartile range, 12-13 months). Participants self-reported HPV vaccination and self-collected anal specimens for HPV DNA testing. We calculated prevalence ratios (PR) for 12-month cumulative incidence and persistence with ≥1 quadrivalent vaccine type (HPV 6/11/16/18) between vaccinated (≥1 dose at baseline) and unvaccinated participants using a propensity score-weighted, modified Poisson regression.

RESULTS

Among 248 participants, 109 (44.0%) were vaccinated at baseline, of whom 62.6% received 3 doses. PRs for HPV 6/11/16/18 were 0.56 (95% confidence interval [CI], .24-1.31) for cumulative incidence and 0.53 (95% CI, .25-1.14) for persistence. PRs were 0.23 (95% CI, .05-1.03) and 0.08 (95% CI, .01-.59) for incidence and persistence, respectively, among participants who received their first dose at age ≤23 years and 0.15 (95% CI, .03-.68) and 0.12 (95% CI, .03-.54) among participants who were sexually active for ≤5 years before vaccination.

CONCLUSIONS

Findings support national recommendations for HPV vaccination at younger ages or soon after sexual debut.

Social networks, high-risk anal HPV and coinfection with HIV in young sexual minority men

OBJECTIVES

Young sexual minority men (SMM) exhibit a high prevalence and incidence of high-risk genotypes of human papillomavirus (hrHPV) anal infections and a confluence of a high prevalence of HIV and rectal STIs. Social determinants of health (SDOHs) are linked to social network contexts that generate and maintain racial disparities in HIV and STIs. A network perspective was provided to advance our knowledge of drivers of genotype-specific hrHPV infection and coinfection with HIV. The study also examined whether socially connected men are infected with the same high-risk HPV genotypes and, if so, whether this tendency is conditioned on coinfection with HIV.

METHODS

Our sample included 136 young SMM of predominantly black race and their network members of other races and ethnicities, aged 18-29 years, who resided in Houston, Texas, USA. These participants were recruited during 2014-2016 at the baseline recruitment period by network-based peer referral, where anal exfoliated cells and named social and sexual partners were collected. Exponential random graph models were estimated to assess similarity in genotype-specific hrHPV anal infection in social connections and coinfection with HIV in consideration of the effects of similarity in sociodemographic, sexual behavioural characteristics, SDOHs and syphilis infection.

RESULTS

Pairs of men socially connected to each other tend to be infected with the same hrHPV genotypes of HPV-16, HPV-45 and HPV-51 or HPV-16 and/or HPV-18. The tendency of social connections between pairs of men who were infected with either HPV-16 or HPV-18 were conditioned on HIV infection.

CONCLUSIONS

Networked patterns of hrHPV infection could be amenable to network-based HPV prevention interventions that engage young SMM of predominantly racial minority groups who are out of HIV care and vulnerable to high-risk HPV acquisition.

Possible Reactivation of Latent Anal Human Papillomavirus Associated with Markers of Immune Dysfunction in Gay and Bisexual Men

BACKGROUND

It is unknown whether reactivation of human papillomavirus (HPV) after latency occurs in the anus. We measured incidence and predictors of incident anal HPV in sexually inactive gay and bisexual men (GBM) as a surrogate of HPV reactivation.

METHODS

The Study of the Prevention of Anal Cancer collected data on sexual behavior, anal cytology, HPV DNA, histology and HPV serology. HPV incidence during periods when zero sexual partners were reported in the last six months at both the current and previous annual visit ("no sexual activity") was analyzed by Cox regression using the Wei-Lin-Weissfeld method to determine univariable predictors.

RESULTS

Of 617 men enrolled, 525 had results for ≥2 visits, of whom 58 (11%) had ≥ one period of "no sexual activity". During sexually inactive periods, there were 29 incident high risk HPV infections in 20 men, which occurred more commonly in older men (Ptrend = 0.010), HIV-positive men (HR = 3.12; 95% CI, 0.91-16.65), longer duration of HIV (Ptrend = 0.028), history of AIDS defining illness (P = 0.010), lower current (P = 0.010) and nadir CD4 count (P = 0.014). For 18 of 29 infections with available results, 12 men remained type-specific HRHPV L1 seronegative. None were consistently seropositive. A new diagnosis of HSIL occurred in only two men, caused by an HPV type other than the incident type.

CONCLUSIONS

Our findings suggest that in sexually inactive GBM, anal HRHPV incidence is relatively common, and is associated with increasing age and immune dysfunction, a pattern consistent with HPV reactivation.

IMPACT

Reactivation of anal HPV may occur.

HPV 16 and 18 contribute to development of anal dysplasia in HIV infection irrespective of gender and sexual orientation

OBJECTIVES

The aim of the present study was too investigate prevalence and persistence of human papilloma virus (HPV) and cytological abnormalities (CAs) in the anal swabs of people living with HIV (PLWH): men who have sex with men (MSM), men who have sex with women (MSW) and women (W).

METHODS

Between March 2010 and January 2019, an anal swab for cytological and HPV genotyping tests was offered to all PLWH attending our clinic. Logistic regression analysis was conducted to identify predictors of infection.

RESULTS

In all, 354 PLWH were screened: 174 MSM, 90 MSW and 61 W. Prevalence of at least one high-risk (HR) HPV was higher in MSM (91%) and W (85%) than in MSW (77%) (P < 0.05). Cytological abnormalities were found in 21.1% of the entire population. At multivariable regression analysis a lower risk for HPV infection was found for W than for MSM [odds ratio = 0.24 (95% confidence interval: 0.115-0.513)] and for MSW than for MSM [0.37 (0.180-0.773)] and there was a significantly higher risk of CAs in PLWH with HPV 16 and 18 [3.3 (1.04-10.49)]. A total of 175 PLWH (103 MSM, 33 MSW and 26 W) had at least one follow-up visit (T1) after a median (interquartile range) follow-up of 3.6 (2.1-5.7) years. The acquisition rate of HR-HPV was high, with 66.7% of PLWH negative for HR-HPV at T0 who became positive at T1 (P < 0.001). The prevalence of CAs was stable (20.6%). A significant association between CAs at T1 and persistence of HPV-16 and/or 18 was found (P < 0.05).

CONCLUSIONS

HPV 16 and 18 are associated with the presence and development of CAs irrespective of sexual orientation.

Efficacy of a carrageenan gel in preventing anal human papillomavirus (HPV) infection: interim analysis of the Lubricant Investigation in Men to Inhibit Transmission of HPV Infection (LIMIT-HPV) randomised controlled trial

BACKGROUND

Carrageenan, a non-toxic gelling agent derived from red algae, has potent anti-human papillomavirus (HPV) activity in in vitro and animal studies. We assessed, in an interim analysis, the efficacy of a carrageenan-based gel in reducing the risk of new detections of anal HPV among gay, bisexual and other men who have sex with men (gbMSM).

METHODS

The LIMIT-HPV study (Lubricant Investigation in Men to Inhibit Transmission of HPV Infection) is a phase IIb, double-blind, placebo-controlled randomised controlled trial conducted in Montreal, Canada. gbMSM were randomly assigned (1:1) to receive a carrageenan-based or placebo gel. Participants were instructed to apply the gel to the anus, condom and/or partners' penis before and-as required-during receptive anal intercourse. Questionnaire data and anal samples were collected at 0, 1, 2, 3, 6, 9 and 12 months. We estimated new detections of anal HPV infection(s) detected via Linear Array using Cox proportional hazards models.

RESULTS

Participants recruited from February 2016 to December 2019 were randomly assigned to the carrageenan (n=127) or placebo (n=128) arm. The efficacy and safety analyses included 201 and 210 participants. The median follow-up time was 7.6 months (range: 0-28.5) in the carrageenan group and 9.3 months (range: 0-40.7) in the placebo group. The HR for new detections was 1.21 (95% CI 0.86 to 1.70): 69.4% and 65.1% new detections of HPV in the carrageenan and placebo arms, respectively. More adverse events were reported in the carrageenan (59.8%) compared with the placebo (39.8%) arm.

CONCLUSIONS

The interim analysis did not demonstrate a protective effect of carrageenan on the risk of new detections of anal HPV infection among gbMSM. Carrageenan gel use was associated with a higher proportion of adverse events. Given these findings and the (assumed) low probability that a beneficial effect would be found by the study's end, the trial was terminated as recommended by the Data Safety and Monitoring Board.

TRIAL REGISTRATION NUMBER

NCT02354144.

Considerations for Child Cancer Survivors and Immunocompromised Children to Prevent Secondary HPV-associated Cancers

Survivors of childhood cancer and other immunocompromised children are at high risk for the development of secondary human papillomavirus (HPV)-associated cancers. In this overview, the authors examine the epidemiology of vaccine efficacy, the natural history of HPV infections, and accelerated HPV-associated cancer development in these populations. The authors highlight the opportunities for preventive care and future research directives.

Sexual behaviours associated with incident high-risk anal human papillomavirus among gay and bisexual men

Objective

High-risk human papillomavirus (HRHPV) causes anal cancer, which disproportionately affects gay and bisexual men (GBM). We examined sexual behaviours associated with incident anal HRHPV in an observational cohort study of GBM in Sydney, Australia.

Methods

GBM aged 35 years and above were enrolled in the Study of the Prevention of Anal Cancer. Detailed information on sexual practices in the last 6 months, including receptive anal intercourse (RAI) and non-intercourse receptive anal practices, was collected. Anal human papillomavirus (HPV) testing was performed at the baseline and three annual follow-up visits. Risk factors for incident HRHPV were determined by Cox regression using the Wei-Lin-Weissfeld method.

Results

Between 2010 and 2015, 617 men were recruited and 525 who had valid HPV results at baseline and at least one follow-up visit were included in the analysis. The median age was 49 years (IQR 43–56) and 188 (35.8%) were HIV-positive. On univariable analysis, incident anal HRHPV was associated with being HIV-positive (p<0.001), having a higher number of recent RAI partners regardless of condom use (p<0.001 for both), preference for the receptive position during anal intercourse (p=0.014) and other non-intercourse receptive anal sexual practices, including rimming, fingering and receptive use of sex toys (p<0.05 for all). In multivariable analyses, being HIV-positive (HR 1.46, 95% CI 1.09 to 1.85, p=0.009) and reporting condom-protected RAI with a higher number of sexual partners (p<0.001) remained significantly associated with incident HRHPV. When stratified by recent RAI, non-intercourse receptive anal practices were not associated with incident HRHPV in men who reported no recent RAI.

Conclusion

GBM living with HIV and those who reported RAI were at increased of incident anal HRHPV. Given the substantial risk of anal cancer and the difficulty in mitigating the risk of acquiring anal HRHPV, HPV vaccination should be considered among sexually active older GBM.

Trial registration number

ANZCTR365383.

Screening Women for Anal Cancers: Guidance for Health Care Professionals

Anal cancer is rare in the general population but is steadily increasing in incidence over the past decade especially in women. Identification and screening of women with high risk facilitates detection of anal precancer and early-stage cancer, improves survival, and potentially uses less invasive therapies compared with the conventional chemoradiation treatments used for advanced cancers. No recently published guidelines currently describe details about screening women for anal squamous cell cancer (ASCC). The available evidence supports the existence of groups of women with higher prevalence of ASCC (e.g., women with human immunodeficiency virus, immune suppression, or previous lower-genital high-grade lesion or cancer) who would likely benefit from screening with some combination of anal cytology and human papillomavirus testing. Additional research is needed to establish the cost-effectiveness and the influence of screening on ASCC mortality rates.

Incidence and Clearance of Anal High-risk Human Papillomavirus Infections and Their Determinants Over 5 Years Among Human Immunodeficiency Virus-negative Men Who Have Sex With Men

BACKGROUND

We aimed to assess the incidence and clearance of anal high-risk human papillomavirus (hrHPV) infections and determinants thereof among human immunodeficiency virus (HIV)-negative men who have sex with men (MSM) over a period of up to 5 years.

METHODS

From 2010 to 2015, HIV-negative MSM were followed every 6 months. Anal self-swabs were collected at inclusion and every 6 months thereafter, and were HPV genotyped using the SPF10-PCR DEIA/LiPA25-system-v1. Incidence rates (IRs) and clearance rates (CRs) of incident anal hrHPV infections were assessed by hrHPV type (types 16, 18, 31, 33, 45, 52, and 58). Determinants of transitions between uninfected and infected states were assessed by hrHPV type using a time-homogenous multi-state Markov model.

RESULTS

This study included 713 HIV-negative MSM, with a median age of 37 years (interquartile range [IQR] 31-43) and a median number of study visits of 6 (IQR 2-7). The IRs of anal infections had a median of 5.2 per 100 person-years (range: 2.2-7.9) across types, with HPV16 having the highest IR. The CRs of incident anal hrHPV infections had a median of 53.7 per 100 person-years (range: 33.4-65.3) across types, with HPV16 having the lowest CR. Having had over 100 lifetime sex partners was significantly associated with incident anal hrHPV infections in multivariable analyses.

CONCLUSIONS

The high incidence and low clearance rates of anal HPV16 infection, compared to other hrHPV types, is consistent with HPV16 being implicated in the large majority of anal cancer cases.

Incidence and Clearance of Anal Human Papillomavirus (HPV)-16 and HPV-18 Infection, and Their Determinants, Among Human Immunodeficiency Virus-Infected Men Who Have Sex With Men in France

BACKGROUND

Prospective data on the natural history of anal human papillomavirus (HPV) infection are scarce in human immunodeficiency virus (HIV)-infected men who have sex with men (MSM).

METHODS

We analyzed incidence and clearance of HPV-16 and HPV-18 in a French cohort of HIV-infected MSM, aged ≥35 years, followed-up annually (n = 438, 2014-2018).

RESULTS

Human papillomavirus-16 and HPV-18 incidence were similar (~10% incident infections at 24 months). Human papillomavirus-16 incidence was higher among high-grade versus no lesion at baseline (adjusted incidence rate ratio = 3.0; 95% confidence interval, 1.07-8.18). Human papillomavirus-16 cleared significantly slower than HPV-18 (32% versus 54% by 24 months).

CONCLUSIONS

In conclusion, anal HPV-16 is more persistent than HPV-18, and its incidence correlates with a prior detection of high-grade lesions.

Lubricant Investigation in Men to Inhibit Transmission of HPV Infection (LIMIT-HPV): design and methods for a randomised controlled trial

INTRODUCTION

Gay, bisexual and other men who have sex with men (gbMSM) have an increased risk of human papillomavirus (HPV) infection and HPV-associated diseases, such as anal cancer and anogenital warts. A carrageenan-based lubricant could prevent HPV infection, thereby reducing the disease burden in this population. This paper describes the protocol for the Lubricant Investigation in Men to Inhibit Transmission of HPV Infection (LIMIT-HPV) study, an ongoing randomised controlled trial (RCT), evaluating efficacy of a carrageenan-based personal lubricant in reducing type-specific anal HPV incidence and prevalence among sexually active gbMSM, efficacy by HIV status, safety and tolerability of the gel and participant adherence to the intervention.

METHODS AND ANALYSIS

The study is a double-blinded, placebo-controlled RCT. Volunteer gbMSM 18 years and older are randomly assigned 1:1 to receive the treatment (a self-applied anal microbicide gel with carrageenan) or placebo (a self-applied placebo gel). At each visit, computerised questionnaires are used to collect data on sociodemographic and clinical variables, lifestyle, sexual behaviour and the gels' safety and tolerability. At baseline and each follow-up visit (months 1, 2, 3, 6, 9 and 12), nurses collect anal specimens tested for 36 HPV types (linear array assay). HIV status is determined at baseline and 12 months. The primary outcome is incidence of type-specific anal HPV infection(s) undetected at baseline. Secondary outcomes are prevalence of type-specific anal HPV infection, safety, tolerability and adherence. We aim to recruit 380 participants to attain the study's objectives. Data will be analysed using intention-to-treat and per-protocol approaches with subgroup analyses by HIV status.

ETHICS AND DISSEMINATION

Ethics approval was obtained by the Research Ethics Boards of McGill University, the McGill University Health Centre, Concordia University and Centre Hospitalier de l'Université de Montréal. Trial results will be disseminated through peer-reviewed publications and conference presentations.

TRIAL REGISTRATION NUMBER

NCT02354144.

HPV infections among young MSM visiting sexual health centers in the Netherlands: Opportunities for targeted HPV vaccination

INTRODUCTION

In 2009, girls-only HPV16/18 vaccination was introduced in the Netherlands which has achieved 46-61% uptake. Heterosexual men have benefitted from herd protection, but it is unknown whether men who have sex with men (MSM) also benefit from herd effects of the girls-only HPV16/18 vaccination program. Because MSM bear a high HPV-related disease burden, countries might consider targeted vaccination for MSM. To study possible herd effects and prior HPV exposure at a potential moment of vaccination, we assessed trends in the HPV prevalence and proportions (sero)negative for the various vaccine types among young MSM visiting sexual health centers (SHCs).

METHODS

We used data from MSM included in PASSYON study years 2009-2017. In this biennial cross-sectional study among visitors of SHCs aged 16-24 years, MSM provided a penile and anal swab for HPV DNA testing (including vaccine types HPV6/11/16/18/31/33/45/52/58) and blood for HPV antibody testing (HPV16/18/31/33/45/52/58).

RESULTS

In total 575 MSM were included, with a median of 22 years of age and 15 lifetime sex partners and 3.5% HIV positive. Trends in penile or anal HPV prevalence during 2009-2017 were statistically non-significant for all vaccine types. Of the 455 MSM with a penile and anal swab, 360 (79%), 283 (62%) and 242 (53%) were HPV DNA negative at both anatomical sites for HPV16/18, HPV6/11/16/18 and HPV6/11/16/18/31/33/45/52/58 respectively. Among MSM who were HPV16/18 and HPV16/18/31/33/45/52/58 DNA negative and were tested for serology (n = 335 and 279 respectively), 82% and 71% were also seronegative for the respective types.

DISCUSSION

There were no significant declines in the HPV prevalence among MSM up to eight years after introduction of girls-only HPV16/18 vaccination, indicating that MSM are unlikely to benefit largely from herd effects from girls-only vaccination. Most MSM were vaccine-type DNA negative and seronegative, suggesting that vaccination of young MSM visiting SHCs could still be beneficial.

Should female sex workers be offered HPV vaccination?

Prophylactic vaccines are efficacious in preventing Human Papillomavirus (HPV) infection and subsequent cervical intraepithelial neoplasia (CIN), cervical cancer, other anogenital cancers, and anogenital warts. Female sex workers (SW) are at increased risk of acquiring sexually transmitted infections, including HPV. There are several reasons to offer HPV vaccination to SW: they are at high risk for HPV and often unvaccinated, and the immunogenicity of the vaccine is also excellent in previously HPV exposed women. Furthermore, women with disease caused by HPV may still benefit from vaccination. The efficacy of vaccinating mid-adult women (26-44 years old) against persistent HPV infection and CIN2+ is good. Although an SW may have been infected or exposed to HPV, she may not have been exposed to all vaccine-included hrHPV types. Vaccination induces mucosal immunity via the production of neutralizing antibodies on the surface of the female genital tract, thus preventing potential transmission to clients. Nevertheless, some considerations argue against offering vaccination to SWs. Current vaccines are only prophylactic and as such, do not affect current HPV infections. Women who have previously cleared HPV infections, may do so again and thus not need vaccination. Fewer SW might be naïve to HPV-types than currently thought. HPV vaccination has probably no effect on latent infections. Vaccinating sometime after sexual debut could be too late, as infections have already occurred. Taken together, some data suggest that vaccination of SW may offer health benefits, also for the community, but sufficient evidence is lacking. In certain cases, HPV vaccination of SW may be recommended. Evidence-based, public health decisions concerning vaccination of SW are challenging and could be facilitated with more research in this high-risk group.

Potential effectiveness of prophylactic HPV immunization for men who have sex with men in the Netherlands: A multi-model approach

BACKGROUND

Men who have sex with men (MSM) are at high risk for anal cancer, primarily related to human papillomavirus genotype 16 (HPV16) infections. At 8.5 per 100,000 per year, the incidence rate of anal cancer among MSM is similar to that of cervical cancer among adult women in the Netherlands. However, MSM are not included in most HPV vaccination programs. We explored the potential effectiveness of prophylactic immunization in reducing anogenital HPV16 transmission among MSM in the Netherlands.

METHODS AND FINDINGS

We developed a range of mathematical models for penile-anal HPV16 transmission, varying in sexual contact structure and natural history of infection, to provide robust and plausible predictions about the effectiveness of targeted vaccination. Models were informed by an observational cohort study among MSM in Amsterdam, 2010-2013. Parameters on sexual behavior and HPV16 infections were obtained by fitting the models to data from 461 HIV-negative study participants, considered representative of the local MSM population. We assumed 85% efficacy of vaccination against future HPV16 infections as reported for HIV-negative MSM, and age-specific uptake rates similar to those for hepatitis B vaccination among MSM in the Netherlands. Targeted vaccination was contrasted with vaccination of 12-year-old boys at 40% uptake in base-case scenarios, and we also considered the effectiveness of a combined strategy. Offering vaccine to MSM without age restrictions resulted in a model-averaged 27.3% reduction (90% prediction interval [PI] 11.9%-37.5%) in prevalence of anal HPV16 infections, assuming similar uptake among MSM as achieved for hepatitis B vaccination. The predicted reduction improved to 46.1% (90% PI 21.8%-62.4%) if uptake rates among MSM were doubled. The reductions in HPV16 infection prevalence were mostly achieved within 30 years of a targeted immunization campaign, during which they exceeded those induced by vaccinating 40% of preadolescent boys, if started simultaneously. The reduction in anal HPV16 prevalence amounted to 74.8% (90% PI 59.8%-93.0%) under a combined vaccination strategy. HPV16 prevalence reductions mostly exceeded vaccine coverage projections among MSM, illustrating the efficiency of prophylactic immunization even when the HPV vaccine is given after sexual debut. Mode of protection was identified as the key limitation to potential effectiveness of targeted vaccination, as the projected reductions were strongly reduced if we assumed no protection against future infections in recipients with prevalent infection or infection-derived immunity at the time of immunization. Unverified limitations of our study include the sparsity of data to inform the models, the omission of oral sex in transmission to the penile or anal site, and the restriction that our modeling results apply primarily to HIV-negative MSM.

CONCLUSIONS

Our findings suggest that targeted vaccination may generate considerable reductions in anogenital HPV16 infections among MSM, and has the potential to accelerate anal cancer prevention, especially when combined with sex-neutral vaccination in preadolescence.