2nd Cervical Cancer Vaccine on the Way?
A second cervical cancer vaccine, shown in a new study to
be highly protective against the sexually transmitted virus that can cause the
disease, may soon be available in the U.S.
In a newly published international trial -- the largest study ever of a
cervical cancer vaccine -- GlaxoSmithKline's Cervarix was found to be more than
90% effective in preventing precancerous cervical lesions over a 15-month
period.
The vaccine protects against infection from the two human papillomaviruses
(HPV) that cause 70% of cervical cancers worldwide.
Pending approval by the FDA, the vaccine could be available for sale in the
U.S. by early next year, a company spokesman tells WebMD.
2 Cervical Cancer Vaccines
If that happens, Cervarix will join Merck's HPV vaccine Gardasil, which has
been on the market in the U.S. since last June.
Both vaccines protect against cancer by preventing infection from the HPV-16
and HPV-18 subtypes, and both require three shots over the course of six months
for full protection.
But both HPV vaccines will not protect against all cervical cancers or all
subtypes of HPV. They will not protect you if have already been infected with
the covered HPV subtypes.
Gardasil also protects against genital warts by targeting two of the HPV
subtypes that cause most of them; Cervarix does not.
James Tursi, MD, of GlaxoSmithKline, tells WebMD that the company chose to
limit the uses for its vaccine in hopes of improving its effectiveness.
"Our hope has been that this vaccine would provide the broadest
protection against cervical cancer, and this is what the data are showing,"
he says.
While the vaccine was designed to target HPV-16 and HPV-18, it also showed
significant cross-protection against two other HPV subtypes that cause one in
10 cervical cancers in the world.
"This is the first time this kind of cross-protection has been shown in
a cervical cancer vaccine trial," he says. "This finding is very
exciting."
Whether Cervarix proves to be more effective for cervical cancer prevention
than Gardasil remains to be seen.
Glaxo is conducting a head-to-head comparison trial of the two vaccines,
with results expected early next year, Tursi says.
Interim Results
The newly reported findings were published in the latest online issue of the
journal Lancet.
They represent an interim analysis from Glaxo's ongoing international trial
evaluating the effectiveness of Cervarix.
A total of 18,644 women from 14 countries were included in the trial. All of
the women were between the ages of 15 and 25 at study entry.
Young girls who are not yet sexually active or who have just become sexually
active are considered the target group for vaccination.
The FDA approved Gardasil for girls and women aged 9 to 26, but Merck is
testing the vaccine in boys because men get genital warts and pass HPV
infection to their partners.
In the Cervarix trial, about half the women received the three-dose
immunizations with the HPV vaccine and half were not vaccinated against
HPV.
After an average follow-up of 15 months, the vaccine was found to be 90.4%
effective against precancerous cervical lesions caused by HPV-16 and
HPV-18.
When researchers further analyzed the lesions they identified, none
occurring in the cervical cancer vaccine recipients were found to be caused by
the two HPV types, indicating 100% effectiveness, Tursi says.
Jorma Paavonen, MD, who is leading the ongoing international trial, tells
WebMD that the interim results are better than he would have expected.
The women in the study will be followed for four years. Women participating
in other studies of the vaccine have been followed for just over five years,
with little evidence of waning protection, he says.
"It is too early to say if boosters will be needed at 10 years or 15
years, but it loks like protection is lasting" he says.
Cervical Cancer Protection for All
An editorial accompanying the study points out that the public health impact
of HPV vaccination is still unclear.
"Certainly vaccinated women will still require cervical screening [Pap
tests] and appropriate follow-up," write Jessica Kahn, MD, and Robert Burk,
MD. Kahn and Burk also questioned whether the women who need a cervical cancer
vaccine most will get it.
"Poverty is strongly associated with high-risk HPV infection and
cervical cancer," they write. "If those who live in poverty cannot
access a highly effective intervention such as HPV vaccines, disparities could
worsen dramatically."
Tursi tells WebMD that Glaxo has been committed to making its vaccines
available to those who can least afford them.
"Glaxo delivers 80% of vaccines to the developing world. We have a
strong commitment to the developing world," he says. "And within the
U.S. in those areas that will require increased attention, we are poised to
provide that."
By Salynn Boyles
Reviewed by Louise Chang
B)2005-2006 WebMD, Inc. All rights reserved