Gardasil safe and effective in young men

Michael Carter
Published: 07 February 2011

The Gardasil vaccine prevents infection and disease associated with high-risk strains of human papilloma virus (HPV) in males, an international team of investigators report in the February 3rd edition of The New England Journal of Medicine.

Sexually experienced boys and young men aged between 16 and 26 were included in the double blind, placebo-controlled study. Among those who received all three doses, the vaccine reduced the risk of lesions associated with high-risk HPV strains (6, 11, 16 and 18) by 90%.

Dr Jane Kim, author of an editorial that accompanied the study, said that its results “affirm the potential for HPV vaccines to prevent related disease in boys and men.”

Infection with human papilloma virus and its associated diseases are common in boys and men. Approximately a quarter of anogenital cancers associated with the infection occur in men, and a disproportionate number of these malignancies occur in gay and other men who have sex with men.

Gardasil has already been shown to prevent persistent infection and disease in girls and women caused by the four strains of human papilloma virus that are associated with a high risk of anogenital cancers. In the US, UK, and many other countries it is recommended that girls receive this or a competitor vaccine before they become sexually active.

To find out about the safety and efficacy of Gardasil in males, investigators designed a study involving 4065 sexually experienced boys and men who were recruited in 18 countries. Each of these individuals reported between one and five lifetime sex partners. They were randomised into two equal groups: one received the vaccine, the other a placebo. These were provided in three doses over a six-month period.

The efficacy of the vaccine at preventing infection with the high-risk strains and disease was examined. Rates of side-effects were also compared between the two groups.

Both heterosexual (3463) and homosexual (602) men were recruited to the study.

Two sets of analyses were performed by the investigators. The first involved all those who were randomised (intent-to-treat); the second was restricted to the 2805 patients who received all three doses of the vaccine or placebo (per protocol).

One month after the administration of the third dose, 97% of those who had received the vaccine had antibodies to all four strains of human papilloma virus.

In the intent-to-treat population, 36 human papilloma virus-related genital lesions occurred in the vaccine group compared to 89 in the placebo arm. This showed that the vaccine had an overall efficacy of 60% at reducing disease.

The vaccine was much more effective in individuals who received all three doses. There were six lesions in the vaccine arm compared to 36 in the placebo arm, an efficacy of 84%.

For heterosexual participants, the vaccine had an efficacy of 92%, but the efficacy was only 79% for those who reported having had at least one male sex partner.

Next the investigators examined the ability of the vaccine to prevent persistent infection with the four strains of virus.

In the intent-to-treat analysis, the vaccine had an efficacy of 48%. For patients who received all three doses, the efficacy was 86%.

Similar proportions of patients in the vaccine and placebo arm reported any side-effect (69% vs. 64%). Most of these were related to mild muscle pain at the site of the injection.

“Our findings point to the efficacy of the quadrivalent HPV vaccine in preventing HPV infection and related diseases in men,” comment the investigators, who conclude that the efficacy of the vaccine in males “may be similar” to that observed in women.

But do their results mean that boys should routinely receive a vaccine against human papilloma virus?

Dr Kim notes in her editorial that data from this study informed the decision to licence use of the vaccine in boys and younger men in the US. Moreover, she believes that the research “undoubtedly gives us cause to celebrate the extraordinary potential for HPV vaccination to improve health in both women and men.”

Nevertheless, she argues that the benefits and costs of routine vaccination in men need to be carefully weighed up. Vaccination of young gay and other men who have sex with men may be cost-effective, but she suggests that, overall, the money spent on routine vaccination could be spent elsewhere where it “could reap even greater health benefits.”

Dr Kim concludes that it is important “to revisit policy decisions as influential new data and new technologies become available, as they undoubtedly will in the case of prevent and control of HPV-related diseases.”

Reference

Giuliano AR et al. Efficacy of quadrivalent HPV vaccine against HPV infection and disease in males. N Engl J Med 364: 401-11, 2011.

Kim JJ. Weighing the benefits and costs of HPV vaccination in young men. N Engl J Med 364: 393-5, 2011.

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