Children who start getting vaccinated against human papillomavirus before 15 need only two doses, the Centers for Disease Control and Prevention decided Wednesday.

Its previous recommendation was for a three-shot regimen, but studies have shown that two doses work just as well. Experts predict that the simpler, more flexible timeline will result in higher rates of HPV vaccination, which has lagged among both girls and boys.

The Advisory Committee on Immunization Practices, which counsels the CDC on the nation’s vaccine schedule, voted Wednesday for the change. Several hours later, CDC Director Tom Frieden accepted the panel's action.

Under the new schedule, the first of two doses of the HPV vaccine should be administered at 11 or 12, although it could be given as early as 9, as under the previous guidance. The second dose would be administered six to 12 months after the first dose.

The new recommendation does not apply to adolescents who begin getting vaccinated after they turn 15. They should still get three shots over a six-month period, the panel said.

The HPV vaccine prevents cervical, vaginal, anal, and head and neck cancers, as well as precancerous lesions and genital warts. The most widely used vaccine is Gardasil, manufactured by Merck.

The rate of HPV inoculation, while increasing in the past year or so, remains below that of other childhood vaccines. Last year, for example, about half of boys ages 13 to 17 had gotten at least one of the recommended three doses, while about 63 percent of girls had gotten at least one dose, according to the CDC.

Cancer experts and public health officials hope a two-shot regimen will boost those figures.

“By reducing the number of doses needed to complete HPV vaccination, it should lead to an increase in the percentage of eligible boys and girls who get vaccinated,” said Douglas Lowy, acting director of the National Cancer Institute. Lowy and his NCI colleague John Schiller developed the technology that underlies the HPV vaccine.

The CDC says that about 80 million Americans are infected with HPV; in most cases, the immune system clears the infection. Still, more than 38,000 cases of HPV-associated cancers occur in the United States every year.

The vaccine is recommended for preteens to ensure protection before they are potentially exposed to the virus by sexual contact. Approved more than a decade ago, it has long been controversial. Some critics have raised safety concerns, while others have suggested that inoculating preteens and adolescents might encourage them to become sexually active early. Subsequent research, however, has shown both issues to be groundless.

Here's why the Center for Disease Control is pushing the flu shot this year. (Monica Akhtar/The Washington Post)

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