Women who only take on dose of the human papillomavirus (HPV) vaccine may still have significant protection from cervical cancer.
New research suggests just one shot could cause HPV-fighting-antibodies to remain present in the blood stream for at least four years, an American Association for Cancer Research news release reported. Preventing HPV can also protect women from cervical cancer.
In 2012 53.8 percent of teenage girls got the first dose of the HPV vaccine, only 33.4 percent received all three shots.
"We wanted to evaluate whether two doses, or even one dose, of the HPV 16/18 L1 VLP vaccine [Cervarix] could induce a robust and sustainable response by the immune system," Mahboobeh Safaeian, Ph.D., an investigator in the Division of Cancer Epidemiology and Genetics at the National Cancer Institute (NCI) said. "We found that both HPV 16 and HPV 18 antibody levels in women who received one dose remained stable four years after vaccination. Our findings challenge previous dogma that protein subunit vaccines require multiple doses to generate long-lived responses."
The researchers looked at Costa Rican women who had, for the most part, received less than the recommended three doses of the vaccine. The team measured the study subjects' antibody levels, which indicated their immune system response to the vaccine.
The team took samples from women who had received one, two, or three doses of the vaccine. They also looked at women who were never vaccinated but had contracted HPV in the past so had leftover antibodies.
All of the women (100 percent) had antibodies against HPV 16 and 18 in their bodies for up to four years. Women who had only received two doses six months apart had comparable antibody levels to those who had taken the full course of treatment.
While the women who had only received one dose of the vaccine had lower antibody levels than those who had taken all three, the levels in both groups were found to be stable.
"Our findings suggest promise for simplified vaccine administration schedules that might be cheaper, simpler, and more likely to be implemented around the world," Safaeian said. "Vaccination with two doses, or even one dose, could simplify the logistics and reduce the cost of vaccination, which could be especially important in the developing world, where more than 85 percent of cervical cancers occur, and where cervical cancer is one of the most common causes of cancer-related deaths."
In several countries such as Chile and British Columbia only two doses of the HPV vaccine are recommended.
"While our findings are quite intriguing and show promise, additional data are needed before policy guidelines can be changed," Safaeian said, referring to the idea that only one does of the HPV vaccine is necessary. "It is important to note that persistence of antibody responses after a single dose has not been evaluated for Gardasil, the quadrivalent HPV vaccine that is more widely used in the United States and many other countries."
