Frequently Asked Questions about HPV Vaccine Safety
- What human papillomavirus (HPV) vaccines are available in the United States?
- What are the known side effects of the HPV vaccines?
- What is an adverse event?
- How was the safety of the HPV vaccines studied before they were licensed?
- Who is in charge of monitoring the safety of vaccines in the U.S.?
- How do the FDA and CDC monitor the safety of vaccines after they are licensed?
- What sorts of mild to moderate adverse events have been reported?
- What sorts of serious adverse events have been reported?
- How do you know if a serious adverse event was caused by the vaccine or not?
- Have FDA and CDC changed their recommendations for the use of the HPV vaccine based on their vaccine safety monitoring?
Two HPV vaccines are licensed by the FDA and recommended by CDC. These vaccines are Cervarix (made by GlaxoSmithKline) and Gardasil (made by Merck).
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 (less than100.4˚F). About 1 person in 30 will get itching where they got the shot. About 1 person in 60 will experience a moderate fever (less than or equal to 100.4˚F to less than102.2 ˚F). These symptoms do not last long and go away on their own.
An adverse event is a health problem that occurs after someone receives 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.
HPV vaccines were studied in clinical trials and found to be safe before they were licensed. For Gardasil, over 29,000 males and females participated in these trials. Cervarix was studied in over 30,000 females participating in several clinical trials performed all over the world. For more information on the clinical trials, see the package inserts for Gardasil and Cervarix.
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. Vaccines manufacturers also often monitor vaccine safety after a product is already approved and on the market.
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 adverse events that were not identified during a vaccine's clinical trials.
- The Vaccine Adverse Event Reporting System (VAERS) receives reports of health problems following vaccination, called "adverse events". VAERS reports can be entered online, or sent by regular mail or fax. 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 get 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 the cause of the adverse event (a possible side effect). It cannot be used to determine definitively if the vaccine caused the adverse event.
- The Vaccine Safety Datalink (VSD) is a collaboration between CDC and several managed care organizations with advanced electronic health records. The VSD works to address gaps in knowledge about rare and serious adverse events that may happen after someone gets a vaccine. The VSD can be used to further study health events detected by VAERS to help determine if a vaccine is causing the adverse event.
- The Clinical Immunization Safety Assessment (CISA) Network is a project between CDC and several academic medical centers in the U.S. which conduct research on adverse events that might be caused by vaccines.
The majority of reported adverse events following HPV vaccination have been considered minor. Reports have included pain and swelling at the injection site, fever, dizziness, and nausea. 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 sitting or lying down for 15 minutes after vaccination.
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 causes GBS.
People have reported blood clots after getting Gardasil. These clots have occurred in the heart, lungs, and legs. Most (over 90%) of these people had a risk of getting blood clots, such as such as smoking, obesity or taking oral contraceptives (the birth control pill).
Some deaths have been reported to VAERS. All reports of death are reviewed by medical doctors at the CDC or FDA. There have been no patterns of death reports that would suggest they were caused by the vaccine.
How do you know if a serious adverse event* was caused by the vaccine?
VAERS staff receives reports of many types of events that occur after vaccination. Some of these events may occur in the time period following vaccination by chance, and some may be caused by vaccination. VAERS staff members are trained to examine the details of each case and look for patterns among the reports. Such patterns might require further study in other data, such as the Vaccine Safety Datalink (VSD).
Have FDA and CDC changed any recommendations for the use of HPV vaccines based on their vaccine safety monitoring?
No vaccine or medicine is completely without risk. CDC and FDA have reviewed all of the safety information available to them on Cervarix and Gardasil. CDC and FDA have determined that Gardasil is safe to use for preventing HPV types 6, 11, 16, and 18 and Cervarix is safe to use for preventing HPV types 16 and 18.
CDC continues to recommend the vaccination of 11 and 12 year old girls with 3 doses of 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 younger.
Additionally, Gardasil protects males against most genital warts. This vaccine is also recommended and available for boys and men, 9 through 26 years of age.
FDA has changed Gardasil’s prescribing information to include information about preventing falls from fainting after vaccination. CDC has taken steps to remind doctors and nurses about this same information.
* An adverse event, as defined by the Code of Federal Regulations, is considered serious if it is life threatening, or results in death, a persistent or significant disability or incapacity, congenital anomaly or birth defect, hospitalization, or prolongation of existing hospitalization.