A US government panel is recommending that preteens get fewer shots of the HPV vaccine against cervical cancer. It is also recommending that the shots be spaced further apart.

Since the HPV vaccine went on sale a decade ago, three doses have been needed. The panel decided that two doses are enough.

"It will be simpler now for parents to get their kids the HPV vaccine series, and protect their kids from HPV cancers," Dr Nancy Messonnier of the Centers for Disease Control and Prevention said.

"Safe, effective, and long-lasting protection against HPV cancers with two visits instead of three means more Americans will be protected from cancer," said CDC Director Tom Frieden. "This recommendation will make it simpler for parents to get their children protected in time."

The vaccine protects against human papillomavirus — or HPV — which can cause cervical cancer, certain other cancers and genital warts. It is commonly spread through sex and, in most cases, the virus doesn't cause any problems. But some infections gradually lead to cancer.

Health officials want kids to get HPV vaccinations at age 11 or 12, well before most first have sex and before they could be infected.

But less than one-third of 13-year-old US boys and girls have gotten three doses. Busy parents have struggled with the old schedule, which called for three trips to the doctor within six months.

The panel is sticking to three doses for anyone who doesn't get their first shot until they turn 15. That's because they didn't have enough data on how well two doses worked in older kids.

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.