Single Dose of HPV Vaccine May Be Enough to Guard Against Cervical Cancer
Researchers found women who only got 1 of 3 recommended Cervarix doses still showed immune response 4 years later
"If you reduce the cost by a third, you can give it to three times as many people," said Dr. Shashikant Lele, clinical chief of gynecologic oncology at Roswell Park Cancer Institute, in Buffalo, N.Y. "If one dose is adequate to protect, we can vaccinate three times the number of women with the same amount of money."
Researchers made these findings during a clinical trial to test the effectiveness of Cervarix in women from Costa Rica.
They measured immune response to the vaccine in blood samples drawn from 78, 192 and 120 women who received one, two and three doses of the vaccine, respectively.
The doctors then compared those results to data from 113 women who were not vaccinated but had antibodies against the viruses in their blood because they had been infected with HPV in the past.
Up to four years later, all of the women in all three vaccination groups had antibodies for HPV 16 and 18, the two strains Cervarix guards against.
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.
Moreover, the levels of antibodies in women from the one- and two-dose groups were between five and 24 times higher than the levels of antibodies in women who were not vaccinated but were infected with HPV.
The contents of the HPV vaccine might provide another explanation, Safaeian said.
The vaccine is created using genetically engineered versions of the virus that prompt an immune response but do not have the ability to multiply and cause illness, she explained.
This type of vaccine might cause a stronger immune response than vaccines made from parts of live viruses (such as the tetanus vaccine) which often require periodic boosting to maintain immunity, Safaeian said.
Debbie Saslow, director of breast and gynecologic cancer for the American Cancer Society, called the findings "very exciting."
"This would be absolutely amazing if we could only give one dose," she said.