The HPV vaccine is used to protect against cervical cancer, which is often caused by HPV infections. The HPV vaccine is currently recommended as a three-dose series, but doctors have found it difficult to complete the series for many girls.
A new study from Costa Rica suggests that a single dose of the human papillomavirus (HPV) vaccine may be enough to protect women against infection with the virus over the long-term.
The study focused on a population of nearly 7,500 Costa Rican women aged 18-25. Although all were supposed to get the recommended three doses of the HPV vaccine at different times, about 20 percent did not.
The researchers 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.
Results were compared with data from 113 women who did not receive vaccination but had antibodies against the viruses in their blood because they were infected with HPV in the past.
Researchers discovered active human papillomavirus antibodies in the women four years after they had received only one dose of Cervarix, a vaccine that protects against two HPV strains.
The study also found that women who received two doses six months apart appeared to have just as much antibody protection against HPV as those who received three doses.
Although antibody levels among women who received one dose were lower than among those who received three doses, the levels appeared stable, according to the researchers, which suggests that these are lasting responses.
In addition, the levels of antibodies in women from the one- and two-dose groups were 5-24 times higher than the levels of antibodies in women who did not receive vaccination, but had prior HPV infection.
"Because of the challenges associated with giving three doses [of HPV vaccine] I think it's very welcomed to see that there's a possibility that the vaccine may not need to be given in a three dose schedule," Dr. Mike Brady, a pediatric infectious disease specialist at Nationwide Children’s Hospital told Live Science.