Insights from the Engage Study: HPV vaccine effectiveness and uptake among gay, bisexual and other men who have sex with men


Human papillomavirus (HPV) is a very common virus that is most easily passed during sexual contact. The body clears most HPV infections on its own, however some become persistent. There are many different types of HPV. Certain types can cause cancer, including anal, cervical and oral cancers. Some types cause anal and genital warts. HPV cannot be cured by medication, but there are vaccines that can prevent a person from getting some types of HPV. All HPV vaccines protect against the two types that cause most cases of anal and cervical cancer (types 16 and 18), and some vaccines protect against additional types more commonly associated with anal and genital warts (types 6 and 11).

HPV among gay, bisexual and other men who have sex with men

Rates of anal cancer are 10 to 20 times higher among gay, bisexual and other men who have sex with men (gbMSM) as a result of higher rates of anal HPV infection. This is one reason why it has become a priority to offer HPV vaccination to gbMSM.

Research has shown that HPV vaccination is highly effective at reducing the risk of anal HPV infection, anal cancer, as well as anal and genital warts among gbMSM. A clinical trial of the 4-valent HPV vaccine (4-valent meaning it protects against four types of HPV) showed that gbMSM who received it were 84% less likely to get a new infection, and 95% less likely to develop a persistent infection, with any of the four HPV types the vaccine covers.

However, to improve our approach to preventing anal cancer in this community, we need to know how well it works in real-world populations, not just among the carefully screened participants of clinical trials. We also need information on the factors that impact whether gbMSM get vaccinated in the first place, and when.

To help fill these gaps in knowledge, researchers from the Engage Study team conducted a series of studies on HPV vaccine effectiveness and uptake among gbMSM in Canada’s three largest cities. 

The Engage Study

Engage is a multi-year cohort study on the sexual health of cis and trans gbMSM. Engage relies on social networks to recruit participants in Toronto, Montreal and Vancouver. Participation involves regular testing for sexually transmitted and blood-borne infections (STBBIs) and a self-administered survey assessing factors that may influence participants’ sexual health. Engage researchers collect and analyse data on a wide array of indicators across prevention, testing and treatment. One of Engage’s major areas of study is HPV vaccine effectiveness and uptake.

HPV vaccine effectiveness among gbMSM

The results from HPV vaccine clinical trials are encouraging. However, as in most clinical trials, participants were screened to minimize factors that could obscure measurement of the vaccine’s effect. This leaves us with limited knowledge of how well the vaccine works, and who it works best for in real-world gbMSM communities.

To help fill these gaps in knowledge, researchers conducted an observational study among 645 sexually active gbMSM, aged 16 to 30 from Vancouver, Toronto and Montreal. The participants answered survey questions and were tested for HPV at the start of the study, then again after 12 months. As an observational study, it did not impose the strict inclusion or exclusion criteria of a clinical trial.

The study found that those who reported having been vaccinated within five years after their first anal sex, were significantly less likely to develop a new or persistent infection with one of the HPV types covered by the vaccine (including the two types that cause most cases of anal cancer). Those who were under 23 years old when they received their first dose were also less likely to experience a persistent infection.

These findings underscore the importance of timing when it comes to HPV vaccination. The younger gbMSM can get vaccinated, the better. The earlier they can get vaccinated relative to becoming sexually active, the better. As such, it is important to explore both why some gbMSM may not be getting vaccinated at all and why some aren’t getting vaccinated early enough to maximize the vaccine’s effectiveness.

HPV vaccine uptake among gbMSM

Knowing how well vaccines work is essential but we can be sure of one thing: they don’t work at all for people who don’t get them. We also need to know how many gbMSM aren’t getting vaccinated, why they aren’t, and what distinguishes them from those who are.

In a longitudinal study conducted between 2017 and 2019, Engage researchers found that only about a quarter of the 2,500 men aged 16 to 80 who participated from Vancouver, Toronto and Montreal had been vaccinated during the three-year time period. Vaccine initiation rates were higher for men aged 26 and younger, at 26% in Vancouver, 33% in Toronto and 35% in Montreal. Among those aged 27 and older, by contrast, the rates were 18% for Vancouver, 26% for Toronto and 7% for Montreal.

Age discrepancy in public coverage

The age discrepancy in vaccine uptake is to be expected, given that HPV vaccination has been provided free of charge for gbMSM under 27 in British Columbia, Ontario and Quebec since 2015/16. This suggests that the cost of the vaccine may be a significant obstacle for gbMSM too old to qualify for public coverage. This is consistent with another finding, namely that older participants who had private health insurance were more likely to have been vaccinated for HPV. These findings highlight a problem in excluding men 27 and older from publicly funded vaccination, as this may hinder community coverage goals and make vaccine access less equitable.

Engagement in sexual health services

Participants were also more likely to have initiated vaccination if they had received other sexual health services, and more than twice as likely if they had visited a sexual health clinic within the previous six months. Initiation was more likely for participants who had tested recently for HIV or another STBBI, recently visited an HIV specialist, or been vaccinated for hepatitis A or B in the past. Interestingly, older participants were more likely to have initiated vaccination if they were currently accessing PrEP.

These findings remind us that engagement of gbMSM in one sexual health service is an opportunity for engagement in others. This is particularly important for those gbMSM whose interactions with sexual health services are infrequent. Every encounter is a chance to share information and explain options so men know there is an effective vaccine, can access it, and (hopefully) decide to get vaccinated. Seizing every opportunity to educate and engage is crucial.

This point is reinforced by another Engage study which showed that, across the three study cities, a sizable proportion of all participants, some 26% to 40% (depending on the city) weren’t aware there was an HPV vaccine and some 7 to 14% (depending on the city) were either undecided or unwilling to get it. Improving these numbers requires knowledge about the obstacles that prevent some gbMSM from knowing about the vaccine and making the choice to get it.

Sexual identity and HPV vaccine uptake

Sexual identity appeared to play a role in both awareness and willingness. Participants who identified as bisexual were both less likely to be aware of the vaccine, and less likely to be willing to get it, than those who identified as gay. One possible reason for this is that sexual health services and information for gbMSM are predominantly tailored to the needs and perspectives of men who identify as gay or queer.

Outness seems to have played a similar role. Participants who preferred to keep their same-sex relationships private were less likely to be aware of the vaccine and less likely to be willing to get it. This makes sense because reluctance to discuss sexual orientation and same-sex experiences greatly limits the possibilities of learning about risk factors and prevention tools through discussions with healthcare providers, community workers and peers. This finding underscores the importance of creating and fostering healthcare spaces where gbMSM can comfortably and securely discuss all aspects of their sexual health, across their lifespans.

Socio-economic factors

Socio-economic factors are also important to mention in any discussion of who is and isn’t getting reached by vaccination, and why. Across all three cities, men who had immigrated to Canada were less likely to be aware of the vaccine. In Vancouver, guys experiencing increasing financial strain were both less likely to be aware and less likely to be willing. In Montreal, having a post-secondary education was associated with awareness and willingness. These socio-economic factors may influence HPV-related outcomes by creating unequal access to the knowledge needed to make informed sexual health decisions.

The Engage Study has provided much-needed evidence that HPV vaccination helps prevent HPV infections linked to anal cancer among gbMSM. Engage has also provided critically important estimates of vaccine uptake among gbMSM, and valuable insights into why it is so low despite the risks associated with HPV and the efficacy of the vaccine. Many gbMSM face barriers to sexual health services, so we need to take every opportunity to raise awareness about HPV vaccination, increase coverage, and cultivate trusting relationships that facilitate engagement and retention in care.


Dr. Ann Burchell is a Canada research chair in sexually transmitted infection prevention at Unity Health Toronto and the University of Toronto. She uses epidemiological data to improve prevention and healthcare services for STIs and minimize their complications.

Dan Miller is CATIE’s knowledge specialist, HIV care and STI. He has a master’s degree in public health from the University of Toronto, and extensive experience working in the areas of health services and public health research and knowledge exchange.


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