but Only 'Modest' Overall Cancer Protection Seen
May 9, 2007 -- The Gardasil vaccine is extremely effective in protecting
women against precancerous lesions caused by the human papillomavirus types
(HPVs) that cause 70% of cervical cancers and most cases of genital warts.
That's the good news from two huge, international clinical trials. The
not-so-good news: Among sexually experienced 15- to 26-year-old women -- some
of whom already have HPV infection -- the vaccine is far less effective in
protecting against dangerous cervical lesions.
The FUTURE 1 trial enrolled nearly 5,500 women aged 16 to 24. The FUTURE II
trial enrolled more than 12,000 women aged 15 to 26. Three-year results from
both trials appear in the May 10 issue of The New England Journal of
Gardasil protects against HPV that is spread mainly during sex. Women often
get HPV infections soon after beginning sexual activity, although most HPV
infections will not develop into cancer. So the best time to get the vaccine is
in the pre-teen years, before age 13.
Or even sooner: The FDA has approved Gardasil for 9- to 26-year-olds, and
the CDC has added it to the childhood vaccination schedule. Several states are
debating making HPV vaccination mandatory for public school attendance,
although all of these measures allow parents to opt out.
In the current studies, the vaccine looked very safe -- and very effective,
says FUTURE II investigator Kevin Ault, MD, associate professor of gynecology
and obstetrics at Atlanta's Emory University.
"The vaccine's efficacy is the biggest news," Ault tells WebMD.
"In FUTURE I, it was 100% effective in preventing precancerous lesions and
genital warts, and in FUTURE II it was 98% effective in protecting against
high-grade, precancerous cervical lesions."
Different Experts, Different Opinions
Ault's numbers reflect the vaccine's effectiveness against the four HPV
strains included in the vaccine -- including cervical-cancer-causing HPV-16 and
But these are only two of the 15 HPV strains known to cause cervical cancer.
An editorial accompanying the studies notes that overall, the vaccine was no
more than 20% effective in protecting women against high-grade precancerous
"This gives us a glimpse of what to expect from vaccinating a generation
of 15- to 26-year-olds regardless of their sexual exposure," the
editorial's co-author, Karen Smith-McCune, MD, tells WebMD. "In that
general population, looking at all women who got the vaccine with all types of
HPV exposure, efficacy in reducing precancer was modest -- 17% fewer cases of
precancer in vaccinated women vs. the placebo group. And if you look at the
most significant precancer, grade 3, there is no significant reduction among
Smith-McCune is associate professor of obstetrics and gynecology at the
University of California, San Francisco. She's also the mother of two
"I am not having my daughters vaccinated because the proven method of
reducing their risk with regular Pap screening is very effective," she
says. "In the absence of safety and efficacy data in the 11- to 12-year-old
age group, and the unknown long-term effect of this vaccine in all age groups,
it is too soon to recommend this vaccine."
Gynecologist Brian Slomovitz, MD, of Weill Cornell Medical Center in New
York, disagrees with Smith-McCune. He says that even with regular Pap
screening, many young women will have to have precancerous cervical lesions
removed -- procedures that may result in pregnancy complications.
"Cervical precancers are a big problem, and genital warts are a huge
problem," Slomovitz tells WebMD. B "The ultimate value of the HPV
vaccine is to reduce deaths due to cervical cancer, but it is also valuable for
preventing high-grade cervical lesions and genital warts."
Ault agrees with Slomovitz.
"These studies are further roof that what we recommended last year was
a good idea: This vaccine should be given to women age 9 to 26," he
Smith-McCune insists that too many questions remain about the HPV vaccine to
recommend widespread vaccination of girls and young women.
"It is important to counter the sense of urgency of vaccinating the
girls with the fact that cervical cancer is not an emergency in the U.S.,"
she says. "Any improvement that will reduce a woman's risk of cervical
cancer is a great thing. We just don't have enough data to support that yet.
The studies are ongoing. We have a lot to learn about the impact of this
vaccine on precancer and cervical cancer."
By Daniel DeNoon
Reviewed by Louise Chang
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