HEALTHY LIVING
09/14/2011 09:42 am ET | Updated Nov 15, 2011

HPV Vaccine Cervarix: 2 Doses Just As Good?

Only got around to getting two of the three doses of the human papillomavirus vaccine Cervarix?

You might still be protected, a new Journal of the National Cancer Institute study suggests.

Researchers from the National Cancer Institute found that women who only got two doses of the HPV vaccine Cervarix were just as protected from the virus as women who got the usual three-shot regimen, after following up four years later.

However, that doesn't mean the findings also apply to people who only got two doses of the Gardasil vaccine, since the formulations for the two vaccines are different, NCI researchers said. Gardasil is more popularly used in the United States; both vaccines are used to protect against the sexually transmitted infection HPV, which causes cervical cancer.

"Further studies are needed to confirm our findings in other populations as well as to quantify the duration of protection for fewer than three doses," study researcher Aimee R. Kreimer, Ph.D., of the NCI Division of Cancer Epidemiology and Genetics, said in a statement.

Cervarix is supposed to be given in three doses over six months. The maximum time length of protection with the vaccine is still to be determined, but the vaccine seems to be effective for at least eight years.

In the U.S., only 32 percent of American girls ages 13 to 17 finished getting all three doses of an HPV vaccine in 2010. Forty-nine percent of girls got at least one dose of the vaccine, according to the NCI.

For this study, researchers observed 7,466 women ages 18 to 25 who were part of the Costa Rica Vaccine Trial who were given either the Cervarix vaccine or a control vaccine for hepatitis A. They found that 20 percent of the women in the study only got one or two doses of either vaccine. And a third of those women didn't finish getting the vaccines because they became pregnant or had cervical abnormalities that may have prevented them from finishing the course of vaccines.

After four years, researchers found that the women who only got two doses of the vaccine were equally protected against HPV strains 16 and 18 as women who got all three doses. One dose of the vaccine also seemed protective, but researchers weren't sure just how effective the protection was.

The safety of the HPV vaccine has come under fire in the past. A 2009 Journal of the American Medical Association study showed that Gardasil is associated with a higher blood clot and fainting risk than other vaccines, and is also linked with unconfirmed deaths, ABC News reported. Some doctors interpreted that as a finding that should spur caution among parents deciding whether to have their children vaccinated, while other doctors interpreted it as a good sign that the vaccine doesn't spur any other unknown health problems.

A recent Institute of Medicine report showed that there is enough evidence to suggest a link between the HPV vaccine and risk of anaphylaxis, a severe allergic reaction that could include hives, nausea, wheezing and difficulty breathing.

Minnesota Rep. Michele Bachmann recently criticized Texas Governor Rick Perry during a recent GOP presidential candidate debate for mandating 11- and 12-year-old girls in Texas to receive the HPV vaccine, the Washington Post reported. (Perry has since apologized for issuing the mandate.) Bachmann also suggested that getting the vaccine could be linked with mental retardation, The Post reported.

From the Washington Post:

“There’s a woman who came up crying to me tonight after the debate. She said her daughter was given that vaccine,” Bachmann said on Fox News. “She told me her daughter suffered mental retardation as a result. There are very dangerous consequences.”

However, the American Academy of Pediatrics issued a statement against the suggested link, saying that "there is absolutely no scientific validity to this statement."

"Since the vaccine has been introduced, more than 35 million doses have been administered, and it has an excellent safety record," according to the AAP statement.

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