Originally published, January 2007. Updated, December 2011.
The "HPV vaccine" was introduced in 2006 to protect young girls against infection with four strains of the human papillomavirus (HPV), two of which are responsible for 70 percent of all cases of cervical cancer. These same strains are known to cause anal cancers and appear to be responsible for throat cancers resulting from oral sex. Rates of both these types of cancer are increasing in both men and women.
The same month that the FDA approved the vaccine (Gardasil) in 2006, a federal advisory panel on immunization practices recommended that all 11 and 12 year old girls be vaccinated. In October 2011 the same committee recommended that boys age 11 and 12 be vaccinated, as well. The shots can be given to boys as young as 9 and to men up to age 26.
More than half of all men and women pick up HPV within a year of becoming sexually active. The vaccine won't work once someone has been exposed to HPV, which is why it is so important to immunize youngsters before they become sexually active.
There are more than 100 strains of HPV, and more than 30 of them are sexually transmitted. Of those, HPV strains numbers 16 and 18 are linked to most cases of cervical cancer as well as to vaginal and vulvar cancers. In 90 percent of all cases, HPV infections clear up on their own and cause no obvious symptoms (except, in some cases, genital warts; the vaccine also protects against the viruses responsible for most of those).
HPV infections that linger can initiate changes that might lead to cancer. Although suspicious cervical changes can be picked up on Pap smears, some 10,000 women in the United States develop cervical cancer every year, and the disease leads to about 3,900 deaths annually. Most of those cases and deaths could be prevented if all women had Pap smears. Worldwide, cervical cancer kills more than 288,000 women per year. Women who are vaccinated and become sexually active will still need Pap smears to check for cervical changes due to other HPV strains. A newer test for HPV is very effective at picking up infections with strains of the virus known to cause cervical cancer. It is approved for testing when abnormalities show up on a woman's Pap test and for use along with Pap tests in women over 30.
The HPV vaccine is given in three shots administered over a period of six months; it will cost $360. (Most private insurers now cover the cost of vaccinating young girls.) According to the FDA, side effects are mild - the worst appear to be some temporary tenderness or pain at the injection site.
While the availability of the vaccine is a big advancement in public health, rates of vaccination of girls in the United States have been disappointing. Many parents object to vaccinating their daughters against a sexually transmitted virus before they become sexually active. But they're missing the point: the vaccine won't work once the sexually transmitted infection occurs. The recommendation to vaccinate boys is likely to be controversial, too, since the cancers in men (anal and throat) due to HPV are associated with homosexual sex. But the vaccine can help protect future female sexual partners of infected males.
Parents now have the opportunity to protect their kids from several types of cancer later in life. The HPV vaccine offers the possibility of saving millions of lives around the world.
Andrew Weil, M.D.