Aug. 14, 2007 -- HPV vaccines can't clear the sexually transmitted virus
from the bodies of women already infected with cervical-cancer-causing HPV
There are many types of HPV (human
papillomavirus). Some types cause cervical cancer, some cause genital warts. Not
every infection results in disease, as the immune system usually fights off the
That's why the CDC's Advisory Committee on Immunization Practices
recommends HPV vaccination for all girls
before they become sexually active. But can HPV vaccination help HPV-infected
women clear the virus?
No, shows a U.S./Costa Rica study led by Allan Hildesheim, PhD, a senior
investigator at the U.S. National Cancer Institute.
"We found there was no difference in the rate of HPV clearance whether or
not women got the vaccine," Hildesheim tells WebMD. "So there is no evidence
this vaccine treats established infections."
The FDA has approved Merck's Gardasil HPV vaccine. Gardasil
prevents infection from four HPV strains: two linked to cervical
cancer and two linked to genital warts. Another HPV vaccine, Cervarix from
GlaxoSmithKline, protects against the same two cancer-linked HPV strains.
Cervarix is approved in Australia; U.S. approval is expected next year.
While the Hildesheim study is testing Cervarix, Hildesheim says Gardasil
studies have also shown that the vaccine cannot speed viral clearance in women
who already have HPV infection.
It is not yet known whether vaccination of already-infected women can
prevent future HPV infections.
Viral clearance means that researchers can no longer detect viral DNA in a
person's blood. It may not mean that the virus is completely eliminated from
the body, says William Bonnez, MD, associate professor of medicine at the
University of Rochester, N.Y. Bonnez, one of the inventors of HPV vaccines,
receives royalties from both GlaxoSmithKline and Merck. He was not involved in
the Hildesheim study.
"HPV vaccination does not affect present HPV infection, but it may prevent
future HPV infections and diseases, regardless of what the present [infection]
status is," Bonnez tells WebMD. "In other words, you do not vaccinate for the
present, but you do it for the future."