Questions and Answers about HPV Vaccine Safety
What are the known side effects of the human
papillomavirus (HPV) vaccine, Gardasil?
The most common side effects are pain and redness where the shot is given (in
the arm). About 1 person in 10 will get a mild fever. About 1 person in 30 will
get itching where they got the shot. About 1 person in 60 will experience a
moderate fever. These symptoms do not last long and go away on their own.
How was the safety of Gardasil studied before it was
The safety of this vaccine was studied in 7 clinical trials before it was
licensed. There were over 21,000 girls and women ages 9 through 26 in the
Who is in charge of monitoring the safety of vaccines
in the U.S.?
Working with healthcare providers throughout the United States, two government
agencies, the Food and Drug Administration (FDA) and the Centers for Disease
Control and Prevention (CDC), monitor the safety of vaccines.
What is an "adverse event?"
An adverse event is a health problem that is reported after someone gets a
vaccine or medicine. It may or may not have been caused by the vaccine or medicine.
For example, the person might get a headache after getting a vaccine. This might
be caused by the vaccine or it might be caused by something else.
How do the FDA and the CDC monitor the safety of
vaccines after they are licensed?
There are 3 systems used to monitor the safety of vaccines after they are
licensed and being used in the U.S. These systems can monitor side effects
already known to be caused by vaccines as well as detect rare side effects that
were not identified during a vaccine's clinical trials.
- The Vaccine Adverse Events Reporting System (VAERS) receives reports of possible
vaccine side effects, called "adverse events" by regular, mail, fax, or
through the web. Reports can be made by doctors, parents or family members,
someone who got a vaccine, or by a manufacturer. Reports can be submitted at
any time after someone gets a vaccine. This means a person can report a
health problem that develops months or even years after they got a vaccine.
All reports are reviewed by trained staff at both FDA and CDC. VAERS
can detect patterns in reports to show that a vaccine might be
causing a possible side effect. It cannot be used to determine for sure if
the vaccine really is causing a side effect.
- The Vaccine Safety Datalink (VSD) Project is a project between CDC and 8
health care organizations. The goal of this project is to address gaps in
knowledge about rare and serious side effects that may happen after someone
gets a vaccine. The VSD can be used to study patterns in reports detected by
VAERS and determine if a vaccine is causing a side effect.
- The Clinical Immunization Safety Assessment (CISA) Network is a project
between 6 academic centers in the U.S. which conduct research on adverse
events that might be caused by vaccines.
How many adverse events have been reported to VAERS
in people who have gotten Gardasil?
From the time the vaccine was licensed through August 31, 2008, over 20 million
doses of Gardasil have been distributed in the U.S. During that time, there have
been 10,326 reports made to VAERS of adverse events following vaccination with
Gardasil. Of these, 94% were classified as reports of mild to moderate adverse
events. 6% have been reports of serious events.
What sorts of mild to moderate adverse events have
The majority of reported adverse events following Gardasil have been considered
minor. Reports have included pain at the injection site, headache, nausea, and
fever. Reports of people fainting have also been received.
Fainting is common after injections, especially in pre-teens and teens. Falls
that occur after someone faints can cause serious injuries, such as head
injuries. To help prevent injuries, CDC and FDA recommend that people receiving
Gardasil (or any other vaccine) should sit or lie down for 15 minutes after
What sorts of serious adverse events have been reported?
Guillain-Barré Syndrome (GBS), which is a rare disorder that causes
muscle weakness, has been reported. To date, there is no evidence that Gardasil
has increased the rate of GBS above that expected in the population.
People have reported blood clots after getting Gardasil. These clots have
occurred in the heart, lungs, and legs. Most of these people had a risk of
getting blood clots, such as taking oral contraceptives (the birth control
27 U.S. deaths have been reported to VAERS as of August 31, 2008. Each of
these deaths has been reviewed and there was not a common pattern to the deaths
that would suggest they were caused by the vaccine. In cases where there was an
autopsy, death certificate, or medical records, the cause of death was explained
by factors other than the vaccine. Some reported causes of death received to
date include illicit drug use, diabetes, viral illness, and heart failure.
How do you know if a serious adverse event was caused
by Gardasil or not?
VAERS staff people receive reports of many types of events that occur after immunization.
Some of these events may occur in the time period following vaccination by
chance, and some may actually be caused by vaccination. VAERS staff members are
trained to examine the details of each case and to look for patterns between
cases. Such patterns might require further study by the Vaccine Safety Datalink.
Have FDA and CDC changed their recommendations for
the use of Gardasil based on their vaccine safety monitoring?
While no vaccine or medicine is completely without risk, CDC and FDA have
reviewed all of the safety information available to them about Gardasil. Based
on this, CDC and FDA have determined that Gardasil is safe to use and effective
in preventing 4 types of HPV.
CDC continues to recommend the vaccination of 11 and 12 year old girls with 3
doses of this vaccine to prevent the types of HPV that most commonly cause
cervical cancer and genital warts. The vaccine is also recommended for girls and
women ages 13 through 26 who did not get any or all of the doses when they were
FDA has changed Gardasil's prescribing information to include information about
preventing falls from fainting. CDC has taken steps to remind doctors and nurses
about this same information. CDC is also adding this information to its
educational materials for parents.
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