Health Information
FDA Approves HPV Vaccine -
Vaccine May Prevent Cervical Cancer
On June 8, 2006, the US Food and Drug
Administration (FDA) announced the approval
and licensure of Gardasil, the first
vaccine designed to prevent both genital
warts caused by the
human papillomavirus (HPV) and
cervical cancer. HPV is the most common
sexually transmitted infection (STI) in the
United States, and the FDA’s rapid 6-month
priority review process reflects the
importance of this new vaccine in combating
disease due to HPV.
Gardasil has
been approved for use by females aged 9-26.
The vaccine is a product of genetic
engineering and is considered safe. Gardasil
does not contain HPV. Rather, it uses a
harmless viral protein to stimulate the
immune system and create resistance against
the virus. It is, therefore, not possible to
become infected with HPV from the vaccine.
What Else Should I Know About Gardasil?
The
immunization is administered as three
intramuscular injections in the upper
arm or thigh over a six-month period–the
second shot is given two months after
the first shot, and the third shot is
given four months later. During clinical
tests, study participants reported only
minor discomfort, which included mild to
moderate pain at the injection site.
Some study participants reported a
low-grade fever after receiving the
vaccine. But overall, evaluations of the
vaccine thus far have not uncovered any
serious adverse effects.
What the Studies Revealed
The
makers of Gardasil, Merck & Co.,
Inc, conducted four double-blind,
placebo-controlled, randomized
trials (one in the United States and
three multinational) that included
21,000 women ages 16-26. These
studies found that Gardasil was
nearly 100% effective at preventing
genital warts caused by HPV
types 6 and 11 (HPV types 6 and 11
cause approximately 90% of genital
warts.)
Most
significantly, the studies also
showed that the vaccine appeared to
offer protection against HPV
types
16 and 18, which cause 70% of
cervical cancers. The vaccine was
found to prevent a precancerous
condition of the cervix known as
cervical
dysplasia, which may lead to
cervical cancer if left untreated.
Although there are other vaccines
capable of reducing the risk of
cancer (eg,
hepatitis B vaccine and
liver cancer), this is the first
vaccine ever developed and marketed
to specifically lower the risk of a
common cancer.
Merck
also conducted two studies measuring
antibody levels for HPV types 6, 11,
16, and 18 in girls ages 9-15 as
compared to females ages 16-26. The
immune response in the younger age
group was similar to that of the
older group, indicating that the
vaccine should have similar
effectiveness across both age
groups.
More Key Points About Gardasil
Gardasil is
not a treatment, but a prevention
measure. The vaccine will not help women
who already have HPV types 6, 11, 16,
and 18. However, most people do not
contract all four at the same time, so
the immunization would still be
recommended as a preventive measure
against the HPV types that a woman does
not have. Also, Gardasil does not
prevent infection with the other HPV
types that are not contained in the
vaccine. Therefore, the vaccine does not
replace the need for routine
Pap smears to screen for cervical
dysplasia and cancer.
Women and
girls allergic to yeast should not be
immunized with Gardasil. Also, although
the clinical trials conducted by Merck
did not show any adverse effects of Gardasil on pregnancy, the product is
not recommended for pregnant women.
Studies are underway to monitor
pregnancy outcomes of women who were
vaccinated with Gardasil during
clinical trials, but did not know they
were pregnant at the time of
vaccination.
Social Implications and Possible
Controversies
The FDA’s
rapid approval process of Gardasil
leaves scientists and the American
public with some lingering questions.
The long-term effectiveness of the
vaccine remains unknown, and only after
follow-up evaluations will its
effectiveness be fully understood. Also,
like any new drug, uncommon and
long-term side effects are unknown until
a generation of users can be observed.
Further studies are being conducted on
the efficacy and safety of Gardasil.
The age that
females should receive the vaccine is
bound to be a sensitive issue. Vaccine
advocates will point out that it is best
for young girls to receive the vaccine
before they become sexually active,
because once they have sex they are at
risk for HPV, and once you contract
HPV
the vaccine is no longer useful.
The FDA’s
approval for the use of Gardasil by
girls as young as age nine acknowledges
statistics showing sexual activity
beginning in adolescence. However, some
parents, teachers, and health officials
may object to adding Gardasil to the
set of routine childhood immunizations
out of concern that children would
interpret such measures as permission to
have sex. Merck is planning to market Gardasil as a cancer prevention
vaccine, not an STI vaccine.
The cost of
the vaccine is expected to be $360 per
three-shot series, which would make it
one of the most expensive vaccines ever
manufactured. This significant cost may
pose problems for state governments
wishing to subsidize the vaccine and
many families.
Gardasil
was not approved for use in men, even
though they are the cause of virtually
all cases of HPV in women. HPV poses no
risk of cancer in men. Merck and other
drug companies are conducting additional
studies evaluating the effectiveness and
safety of Gardasil for males.
More on HPV: What It Is, Who Is At Risk,
and How You Get It
The human
papillomavirus lives on the skin or
mucous membranes of infected
individuals. Approximately 20 million
Americans are infected with HPV. The CDC
estimates that 6.2 million Americans are
newly infected with genital HPV each
year, and that over 50% of sexually
active men and women will acquire an HPV
infection at some point in their lives.
By age 50, approximately 80% of American
women will have become infected with
HPV. Over 630 million people are
infected with HPV worldwide.
Although
HPV
is extremely prevalent in the United
States, most people have never heard of
it. This is because there are often no
symptoms, and many cases go away on
their own. Although the body’s immune
system is often effective in getting rid
of many types of HPV, other types of HPV
can cause genital warts and, more
seriously, cervical dysplasia, a
precancerous condition. Fortunately, the
vast majority of HPV infections,
or
lesions do not
lead to cervical cancer.
The
transmission rate of HPV is high because
most people who are infected don’t know
that they have HPV and therefore don’t
take necessary precautions. Even more
importantly, HPV is spread by
skin-to-skin contact and not via blood
or bodily fluids like most other STIs.
Anyone who has ever been sexually active
bears the risk of getting and passing on HPV. Because there are no symptoms, a
person can have HPV for years and not
know they are transmitting it through
genital contact.
Condoms are not
entirely effective in preventing HPV
infection because areas that are not
covered may be infected. However, condom
use has been associated with a lower
rate of cervical cancer.
RESOURCES:
Centers for Disease Control and Prevention
www.cdc.gov
National Cancer Institute
www.cancer.gov
National Institute of Allergy and Infectious
Disease
www.niaid.nih.gov
US Food and Drug Administration
www.fda.gov
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