incidence of anal human papillomavirus (HPV) are high among young gay men, according
to US research published in the Journal
of Infectious Diseases. Overall prevalence of anal HPV infection was 70%, and
HPV 16 and/or HPV 18 – the HPV
types most associated with anal cancer – were detected in 37% of study participants.
believe their research shows the importance of vaccinating young gay men before
they become sexually active. However, none of the men were infected with all
four HPV types covered by the quadrivalent vaccine Gardasil, therefore showing that immunisation would still be worthwhile
for young gay men who are sexually experienced.
highlight the need to immunize YMSM [young men who have sex with men] prior to
their sexual debut, something that will likely require universal male
immunization,” write the authors. “At the same time, the fact that most YMSM
appeared to remain susceptible to at least some HPV types included in the
vaccine, catch-up immunization programs do offer YMSM some benefit.”
Rates of anal
cancer are higher among gay men than other groups. The cancer is associated
with persistent infection with high-risk HPV types. Gardasil provides a high degree of protection against the two most
common cancer-associated HPV types (16 and 18). In the US, immunisation with
this product is now recommended for all males aged between eleven and 21 years
and for gay and other men who have sex with men up to the age of 26 years.
recommendations, little is currently known about prevalence and incidence of
anal HPV infection among young gay men. Investigators in Seattle therefore
undertook a prospective study lasting one year involving 94 gay men aged between
16 and 30 years. These participants had anal swabs at baseline, and again after six
and twelve months, to check for HPV infection and HPV type. The authors also
looked at the factors associated with HPV infection and knowledge of HPV and
HPV vaccination. They were hopeful that their findings would inform vaccination
Most of the men
were white (60%) and their median age was 21 years. Nearly all participants
reported a history of at least one episode of insertive anal sex (88%) and
receptive anal sex (92%). The median age of first anal sex with another man was
18 years. The median number of lifetime, anal-sex, insertive partners was two and
the median number of receptive anal sex partners was three.
Overall, 70% of
men had anal HPV infection detected at some point during the study. HPV 16 was
the type with the highest prevalence (28%).
Among the men who
did not have the infection at baseline, the incidence of new anal HPV infection
was 39 per 1000 person-months.
HPV 16 and/or 18
infections were detected in 37% of men over the course of the study, with an incidence of
15 per 1000 person-months.
fifth of participants (19%) had persistent HPV 16 or 18 infection, with the same
strain detected in consecutive swabs.
Half of all
participants had at least one of the HPV strains covered by Gardasil detected at some point during
the study. However, no participant tested positive for all four types and only
3% had evidence of acquiring both HPV 16 and 18 at the same time during
A total of 48 men
with any prevalent HPV infection provided two or more swabs. Most of these men
(81%) cleared one or more HPV type during follow-up. Half the 18 men with
HPV 16 cleared the infection, as did 67% of those with HPV 18.
The prevalence of
HPV infection, including the high-risk types, increased with higher numbers of
male anal sex partners. Among the men reporting one lifetime anal-sex partner
at baseline, 35% had any anal HPV infection and 6% were infected with HPV 16
and/or 18. Among men with two or more partners, there was a 35% prevalence of
anal HPV 16 and/or 18 infection.
For each additional
partner in the previous three months, the risk of prevalence infection
increased by a quarter (OR = 1.24; 95% CI, 1.00-1.57) and the odds of incident
infection by a third (OR = 1.32; 95% CI, 1.03-1.70).
moderately good knowledge of HPV among the participants, with 76% of men
reporting that they had heard of the infection. However, only 34% knew that it
was the cause of anal cancer and 6% correctly identified the virus as a cause
of oral and throat cancers.
three-quarters of participants had heard of Gardasil.
The investigators explained the vaccine’s treatment course, side-effects and
efficacy to the participants, after which 93% of men said they would be
extremely or somewhat interested in the vaccine if it were available free of charge.
“We observed a
high prevalence and incidence of anal HPV infection,” comment the authors,
“HPV-16 and/or -18, the two strains that cause the majority of anal cancers,
was detected in over one-third of study participants at least once during the
year of follow-up, and nearly 20% of all YMSM in our study had evidence of
persistent infection with one of these two strains.”
believe their findings have implications for HPV vaccination strategies: “Given
the very high prevalence of HPV infection among YMSM, many (if not most) have
been exposed to infection from one of their first few partners, a finding that
highlights the desirability of immunizing YMSM before they become sexually
active.” Nevertheless, they also believe that men who are sexually active would
also benefit from vaccination.