One HPV Shot Might Provide Long-Term Protection

HPV vaccine Cervarix may be effective enough after just one dose

/ Author:  / Reviewed by: Robert Carlson, M.D Beth Bolt, RPh

(RxWiki News) It may never be possible to find a "cure for cancer" — even better would be preventing cancer in the first place. That's what the HPV vaccine can help do.

A recent study found that receiving even one dose of the HPV vaccine may be enough to protect women from infection.

Human papillomavirus, or HPV, is a sexually transmitted viral infection. Two types of HPV, called HPV-16 and HPV-18, can cause cervical cancer and other cancers.

Cervical cancer is a common cancer that kills women across the world.

It is currently recommended that women receive three doses of the HPV16/18 vaccine, known as Cervarix.

"Ask your doctor about the HPV vaccine."

This study, led by Mahboobeh Safaeian, PhD, of the National Cancer Institute, looked at the effectiveness of the HPV vaccine based on how many doses women received.

The researchers divided 390 Costa Rican women into four groups to receive the HPV16/18 vaccine.

One dose was administered to 78 of these women. Meanwhile, 140 women received two doses of the vaccine with one month between doses.

Two doses, with six months between them, were administered to 52 women, and 120 women received three scheduled doses, the recommended amount.

A vaccine works by causing the body to make antibodies, or disease-fighting cells, that specifically target a disease.

The researchers measured how many antibodies, that were specific to HPV-16 or HPV-18, in the women at the start of the study (before vaccination) and then after they were vaccinated.

In addition, the women's antibodies against HPV-16 and HPV-18 were measured once a year for an additional four years after getting the vaccine.

The level of antibodies was compared among these women and against another group of 113 women.

The group of 113 women had antibodies against either HPV-16 or HPV-18 because they had previously had a natural infection from the virus.

At the end of the four year period, all of the women in all four vaccination groups still had antibodies against both HPV-16 and HPV-18.

The researchers found that the average levels of antibodies in the women who received two doses of the vaccine at six months apart were no lower than the levels in the women who received three doses.

When the researchers compared the vaccinated women to the women who had experienced natural HPV infections, the researchers found that the vaccinated women actually had better immunity to the infection.

The average antibody levels of the women who received two doses of the vaccine were 24 times higher than the antibody levels of the naturally infected women for HPV-16 and 14 times higher for HPV-18.

Even among women who received only one dose of the HPV vaccine, average antibody levels were nine times higher than those in the naturally infected women for HPV-16 and five times higher for HPV-18.

"Antibody levels following one dose remained stable from month 6 through month 48," the researchers wrote. "Results raise the possibility that even a single dose of HPV [vaccine] will induce long-term protection."

The study was published November 4 in the journal Cancer Prevention Research. The research was funded by the National Cancer Institute, the National Institutes of Health Office of Research on Women's Health and the Ministry of Health of Costa Rica.

The vaccine used in the trial was provided by GlaxoSmithKline Biologicals, which also provided supports for aspects of the trial required by the US Food and Drug Administration.

One author received royalties on US government-owned patents. Another is an inventor of US government-owned HPV vaccine patents that have been licensed to GlaxoSmithKline and Merck and received limited royalties.

A third author has a GSK agreement with the National Cancer Institute, and a fourth has ownership interests in DDL Diagnostic Laboratory. No other potential conflicts of interest were reported.

Review Date: 
November 6, 2013
Last Updated:
December 30, 2013