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Update on HPV vaccine: Will males be the next ones to receive immunization?
Research indicates vaccine can prevent HPV infection in men
Results from a Phase III study in men ages 16 to 26 indicate that the human papillomavirus (HPV) vaccine Gardasil (Merck & Co.) prevented 90% of external genital lesions caused by types 6, 11, 16, and 18 of HPV.1
Merck was scheduled to submit an application to the Food and Drug Administration (FDA) before the end of 2008. The company is seeking approval to market Gardasil for use in males ages 9-26 to prevent genital warts and precancerous growths.
Why vaccinate men against HPV? HPV is one of the most common sexually transmitted diseases (STDs) and is frequently presented clinically as anogenital warts in males and females.2 There is a high rate of transmission of HPV in female partners of men with pre-existing penile warts, and HPV infection in men has been shown to contribute to HPV infection and subsequent cervical disease in women.2
Some types of HPV can cause penile cancer or anal cancer. Researchers also have found that many oral cancers in men are associated with HPV; a 2008 clinical trial designed to test therapies for advanced tongue and tonsil cancers found that more than 40% of the tumors in men were infected with HPV.3
In weighing the use of HPV vaccine in men, officials will look at "herd immunity." If large numbers of girls and women do not obtain the recommended vaccinations, then vaccination of men and boys could play a significant role in lowering infection rates among males and females.4
To examine use of the Gardasil vaccine in men, scientists designed the Phase III study to determine the efficacy of the vaccine in males against HPV types 6-, 11-, 16-, and 18-related external genital lesions, a composite endpoint that included genital warts (condylomata); penile/perineal/ perianal intraepithelial neoplasia (PIN); and penile/perineal/perianal cancer.
In performing the analysis, researchers looked at about 3,400 heterosexual males ages 16 through 23, as well as 600 men ages 16-26 who have sex with men. Men participating in the study were randomized in a 1-to-1 ratio to receive Gardasil or placebo at day one, two months, and six months, with 36 months of planned follow-up. At the time of vaccination, participants had no evidence of genital lesions, no history of genital warts, and five or fewer lifetime sexual partners.
Results indicate the vaccine was 90.4% effective at reducing external genital lesions [three cases in the vaccine group vs. 31 cases in placebo group; 95% confidence interval (CI): 69.2, 98.1; p-value < 0.001]. The three cases seen among those vaccinated were caused by genital warts, resulting in the vaccine being 89.4% effective in preventing genital warts (95% CI: 65.5, 97.9). For PIN, there were no cases in the vaccine group vs. three cases of PIN 1 or PIN 2/3 in the placebo group. No cases of penile/perineal/perianal cancer were detected in the vaccine or placebo group. The study had a mean duration of about 29 months at the time of the analysis.
No vaccine-related serious adverse events were reported in the study. Scientists did note a slightly higher proportion of study participants with injection-site adverse events in the vaccine group (60.1%), compared to placebo (53.7%).1
More girls get shot
About 25% of adolescent females received at least one dose of the HPV vaccine in 2007, according to estimates released by the Centers for Disease Control and Prevention (CDC).5 This was the first year for HPV immunizations to be tracked in the National Immunization Survey. The HPV vaccine received FDA approval in June 2006.
The immunization numbers are good for the first year of the vaccine, says Lance Rodewald, MD, director of the Division of Immunization Services at the CDC's National Center for Immunization and Respiratory Diseases.
When another adolescent vaccine, meningococcal conjugate vaccine (Menactra, Sanofi Pasteur; Swiftwater, PA), was introduced, its first-year uptake was about 11%, says Rodewald. By the second year, it grew to 32%. For the HPV vaccine to record a 25% uptake in the first year is promising, he says.
"It always takes a few years for a vaccine to be widely accepted, but we were pretty pleased with this as an initial one," Rodewald says. "But obviously, we're not going to be satisfied until we have high coverage."
Look to a possible announcement on the status of a potential HPV vaccine candidate. Results of a Phase III study of Philadelphia-based GlaxoSmithKline's Cervarix are on track for completion/data submission to the FDA in the first half of 2009, confirms Liad Diamond, company spokeswoman. The company decided to augment its FDA application with the addition of the Phase III study data so they may be included in the U.S. label.
The Cervarix vaccine has been approved in 67 countries, including Mexico, Australia, Singapore, the Philippines, and the 27 member countries of the European Union.
The vaccine is targeted to prevent infection and lesions from the two most prevalent cancer-causing types of HPV, types HPV 16 and 18. It is formulated with AS04, a proprietary adjuvant system designed to sustain antibody levels over time.
Published research indicates that the vaccine demonstrated protection up to 4.5 years against persistent infection with HPV 16 and HPV 18 and protection from pre-cancerous lesions.6 Protection also was demonstrated against infection with the third and fourth most prevalent cancer-causing types of HPV, types 45 and 31.6
Scientists also are eyeing use of the Cervarix vaccine candidate in young men. Research looked at 181 Finnish males ages 10-18 randomly assigned to receive Cervarix or a hepatitis vaccine. Findings indicate that Cervarix was effective, but individuals who received it were more likely to report pain and swelling after injections. However, vaccine-related symptoms did not affect compliance with the three-dose course, which was equally high (97%) in both groups.7