Once may actually be enough when it comes to providing long-term protection from human papilloma virus. According to a new study involving women from Costa Rica, women and girls may only need to get one dose of the HPV vaccine rather than the current recommended series of three shots.
Researchers, led by Mahboobeh Safaeian, Ph.D an investigator in the Division of Cancer Epidemiology and Genetics at the National Cancer Institute (NCI) in Bethesda, Md. found that a study of Costa Rican women who received just one dose of a human papillomavirus vaccine had antibodies in their blood against the HVP virus which stayed stabile even four years after receiving the shot, “suggesting that a single dose of vaccine may be sufficient to generate long-term immune responses and protection against new HPV infections, and ultimately cervical cancer, “ she stated. In fact, those who were given one dose (as opposed to the standard three) had an immune response that was between 5-9 times more potent than seen in those who had been naturally infected with HPV, although the levels were still below those who had received either 2 or three doses.
Safaeian’s team specifically looked for the presence of an immune response to the vaccine (measured by antibody levels) in blood samples drawn from 78, 192, and 120 women who received one, two, and three doses of the vaccine, respectively, then analyzed them against data from obtained from 113 women who hadn’t gotten vaccinated, but had developed antibodies against the viruses after being infected naturally.
"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," she stated. "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."
While more research needs to be done, the findings are considered very promising for being able to provide cheaper vaccinations around the world by reducing the number needed, especially in the third world where more than 85% of all HPV cases are found. At present, British Columbia and Chile are already using only two doses as part of their protection programs.
Note: Safaeian noted that they have yet to evaluate persistence of antibody responses after a single dose for Gardasil, used primarily in the US.