Two Doses of HPV Vaccine May Work as Well as Three
U.S. government researchers find fewer shots offer just as much protection against cervical cancer.
Sept. 8 (HealthDay News) — Two doses of the human
vaccine may offer just as much protection against cervical cancer as the
three-dose regimen now being used, new U.S. government research shows.
The findings stem from an
analysis of data from the National Cancer Institute's Costa Rica Vaccine Trial,
in which 7,466 women were enrolled, according to a news release from the Journal
of the National Cancer Institute, which published the results on
The women were either given the HPV
vaccine Cervarix or a Hepatitis A vaccine. Although researchers intended to
give the women receiving Cervarix the full three doses, 20 percent of them got
only one dose or two doses for a variety of reasons.
After four years, the
researchers found, two doses of Cervarix offered the same level of protection
against HPV infection as three. Even one dose offered a high level of
While the researchers said
that more studies are needed to evaluate the long-term effectiveness of the
fewer doses, they wrote in a journal news release: "Our clinical efficacy
data provide suggestive evidence that an HPV vaccine program that provides
fewer doses to more women could potentially reduce cervical cancer incidence
more than a standard three-dose program that uses the same total number of doses
but in fewer women."
Cervarix is one of two
vaccines approved by the U.S. Food and Drug Administration to protect against
the two types of HPV, 16 and 18, that are responsible for 70 percent of
cases around the world every year.
The analysis was led by
Aimee R. Kreimer, of the division of cancer epidemiology and genetics at the
U.S. National Cancer Institute.
In an editorial
accompanying the journal article, Cosette Marie Wheeler, of the University of
New Mexico, noted, "The age-old adage of less is more may apply to HPV
vaccination, and if so, the report ... represents an important step on the road
to more effective and sustainable cervical
cancer prevention programs."