The human papillomavirus vaccine prevented infections from the most dangerous virus types among women over 26 who had not been previously infected, the seven-year study of thousands of women found.
“If a person has not been exposed to a virus type before, the vaccine is highly efficacious in a broad age range of women,” said Cosette Wheeler, lead author of a June 28 report published in the online edition of Lancet Infectious Diseases.
The human papillomavirus, or HPV, vaccine is FDA-approved for women only through age 26, although doctors can legally offer the shot to older women as an “off-label” use.
The primary target for HPV vaccinations is boys and girls ages 11 and 12 for routine vaccinations and for “touch-up” vaccinations up to 21 for males and 26 for females, Wheeler said.
HPV is among the most common sexually transmitted diseases, and more than 40 types can infect male and female genitalia. Half of U.S. residents will be infected with HPV in their lifetimes, the Centers for Disease Control and Prevention estimates.
Infections from five types of HPV cause about 85 percent of invasive cervical cancers.
The decision to target children in their early teens is primarily one of cost versus benefit, Wheeler said.
Officials who want the greatest benefit from limited public-health dollars urge vaccinating children before they become sexually active.
“The vaccine is more efficacious prior to exposure,” she said.
The high cost of HPV vaccine is a key factor in the discussion.
A single dose of the vaccine costs $130 to $150, and insurance is unlikely to cover it for off-label uses. For children, the CDC recommends a three-dose sequence.
Among those who are not vaccinated, many develop natural immunity through exposure to HPV after they become sexually active. As a result, HPV infection rates decline as the population ages, she said.
In other words, society gets the greatest bang for its health-care dollars by vaccinating children before they become sexually active.
“It does not change the fact that older women benefit from vaccinations,” though in smaller numbers, she said. “The benefit may be small, but if we really wanted to eradicate cervical cancer like we did smallpox, you would vaccinate as many people as you could afford to.”
The study, which tracked women ages 26 to 45 for seven years, found that the vaccine was about 90 percent effective in preventing infection from two of the most dangerous HPV types.
The study draws no conclusions about what groups of older women could benefit the most from the vaccine. Nor does it recommend any changes in the FDA guidelines for the vaccine.