SAN FRANCISCO – So few girls are receiving the human papillomavirus vaccine that vaccinating boys is becoming cost effective, according to Dr. Janet A. Englund.
That’s an important message from recent data on human papillomavirus (HPV) vaccination rates and cost-effectiveness studies, Dr. Englund said at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy.
Federal data show "quite low uptake in girls" in each of the past 3 years, "which makes it important to push for increased vaccination of boys," not only to protect males against genital warts and HPV-associated cancers but to increase protection for girls, she said.
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A recent study shows that vaccinating boys for HPV is becoming cost effective because so few girls are getting vaccinated.
The percentage of U.S. adolescents who received at least one dose of HPV vaccine increased from 69% in 2010 to 78% in 2011, but the proportion of U.S. girls who got all three recommended doses was only 32% in 2010 and 35% in 2011 (MMWR 2012;61:671-7).
That’s "disappointing" compared with larger increases in the use of other vaccines in U.S. girls in the same time period and in comparison with HPV vaccination coverage in other countries, said Dr. Englund, a specialist in infectious diseases at Seattle Children’s Hospital and professor of pediatrics at the University of Washington, Seattle. She was a member of the Advisory Committee on Immunization Practices (ACIP) during much of the time HPV vaccine issues were discussed.
School-based vaccination programs have produced HPV vaccination series coverage rates of 56%-85% in Canadian provinces, 80%-90% in the United Kingdom, and greater than 90% in Australia. The United States does not have a school-based vaccination program. Four years after the HPV vaccination program was started in Australia, genital warts have nearly disappeared in young women and men, one study found (Sex Transm. Infect. 2011;87:544-7).
In late 2011, ACIP recommended routine use of HPV vaccine in boys aged 11-12 years. Studies have shown that immunogenicity after the quadrivalent vaccine series is more than doubled if males get vaccinated at ages 9-15 years compared with 16-26 years, she said at the meeting, sponsored by the American Society for Microbiology. For both boys and girls, the vaccine is most effective if given prior to becoming sexually active.
In males, pivotal trials found efficacy rates for the quadrivalent HPV vaccine to be 89% in previously uninfected males and 67% regardless of infection status at baseline.
Dr. Janet A. Englund
"These vaccines remain quite expensive," but they are cost effective in the United States, she said.
Analyses presented to ACIP in 2009 suggest that the HPV vaccine’s cost per quality-adjusted life year (QALY) gained for 12-year-old girls ranges from $3,000 to $45,000, depending on the model used in the analysis, Dr. Englund said.
If just the prevention of cervical disease is considered, the cost of adding HPV vaccinations for males seems too costly, adding $115,400-$182,400 in cost per QALY. But if the vaccine’s benefits in reducing vulvar and vaginal cancers, genital warts, anal cancer, recurrent respiratory papillomatosis, oropharyngeal cancer, and penile cancer are also considered, the cost per QALY when vaccinating males drops to $24,400-$42,700. In the United States, costs below $50,000 per QALY are generally considered to be cost effective, Dr. Englund said.
Other analyses suggest that vaccinating boys against HPV is cost effective when the immunization rate for girls is low, "which it is in the United States," she said. "Although coverage in females is increasing, we believe that male vaccination would remain cost effective into the foreseeable future." When female coverage reaches high levels, male vaccination likely would not be cost effective.
Between 2004 and 2007, invasive cancers associated with HPV types 16 and 18 were diagnosed in more than 11,000 men and more than 20,000 women in the United States, data presented to ACIP in 2011 showed.
One study that enrolled freshmen at the University of Washington found approximately a 50% cumulative incidence of HPV in males during the next 24 months, she added.
The most common adverse events in males after vaccination are injection-site reactions. Dr. Englund said that serious adverse events have been minimized in her office by having the adolescents sit down for half an hour, or at least 15 minutes, before leaving the office.
Dr. Englund has been a consultant for GlaxoSmithKline (which markets an HPV vaccine) and Novavax and has received research support from Novartis and Chimerix.