Frequently Asked Questions about HPV Vaccine Safety
- Are human papillomavirus (HPV) vaccines safe?
- What HPV vaccines are available in the United States?
- How is the safety of HPV vaccines monitored and evaluated in the United States?
- What is an “adverse event?”
- Have serious adverse events been reported after people receive HPV vaccines?
- Do HPV vaccines cause ovarian failure?
- Has anyone died after receiving HPV vaccines?
- Is fainting common after receiving HPV vaccine?
- Is there pain associated with HPV vaccines?
- Have FDA and CDC changed any recommendations for the use of HPV vaccines based on their vaccine safety monitoring?
- Where do I go to learn more about HPV vaccines?
There have been many studies conducted to determine the safety of HPV vaccines in the United States. An overview of these studies can be found here http://www.cdc.gov/vaccinesafety/Vaccines/HPV/Index.html#data. One study found an increased risk for fainting (also known as syncope). However, there were no serious safety concerns found in any of these studies.
One lot of Gardasil® vaccine was recently recalled by the manufacturer, although no concerning adverse events have been seen among people vaccinated with this lot. For more information, click here.
There are two human papillomavirus (HPV) vaccines that are licensed for use in the United States by the U.S. Food and Drug Administration (FDA) and recommended by the Centers for Disease Control and Prevention (CDC). These vaccines are Cervarix® (made by GlaxoSmithKline) and Gardasil® (made by Merck). Both vaccines are designed to protect against the two HPV types that cause most cervical cancers. Gardasil also protects against genital warts. The safety of Gardasil was studied in clinical trials with 29,000 females before it was licensed. The safety of Cervarix was studied in clinical trials with more than 30,000 females before it was licensed.
To find out more about the benefits of HPV vaccination, please visit www.cdc.gov/HPV.
All vaccines used in the United States are required to go through years of extensive safety testing before they are licensed by FDA. Once in use, they are continually monitored for their safety and effectiveness.
Both HPV vaccines – Gardasil® and Cervarix® -- are currently being monitored for any adverse events, especially rare events not identified in the pre-licensure studies.
CDC uses three systems to monitor and evaluate the safety of vaccines after they are licensed: the Vaccine Adverse Event Reporting System (VAERS), the Vaccine Safety Datalink (VSD), and the Clinical Immunization Safety Assessment (CISA) Network.
Because Gardasil®, accounts for 99 percent of the doses that are distributed in the United States, almost all of CDC’s HPV vaccine safety monitoring and research has been focused on this vaccine.
An adverse event is an undesired side effect or health problem that occurs after someone receives a vaccine or medicine. It may -- or may not -- have been caused by the vaccine or medicine.
From June 2006-March 2014, approximately 67 million doses of HPV vaccines were distributed in the United States. VAERS received approximately 25,000 adverse event reports occurring in girls and women who received HPV vaccines. As described above, an adverse event is an undesired side effect or health problem that occurs after someone receives a vaccine or medicine. It may -- or may not -- have been caused by the vaccine or medicine. Of the reports to VAERS, 8 percent were classified as “serious”. Among VAERS reports, the most frequently reported symptoms were: fainting, dizziness, nausea, headache, fever, hives, and localized pain, redness, and swelling at the sight of the injection. For more information, see Morbidity and Mortality Weekly Report (MMWR): “Human Papillomavirus Vaccination Coverage Among Adolescents, 2007–2013, and Postlicensure Vaccine Safety Monitoring, 2006–2014 — United States”
Since Gardasil® has been licensed in the United States, CDC and FDA have continually monitored its safety. CDC and FDA have found no reason to be concerned that Gardasil® may be causing premature ovarian failure (a condition in which a woman’s ovaries no longer function as they should).
Premature ovarian failure has many causes, including genetic, infectious, inflammatory, autoimmune, and toxin-related, but in many cases no cause is identified. As of July 2013, VAERS has only received two reports of premature ovarian failure following receipt of the Gardasil® vaccine in the United States. VAERS has received six reports of related conditions (4 reports of “premature menopause” and 2 reports of “ovarian disorder”) after Gardasil® vaccination. When health problems happen after vaccination, it does not necessarily mean they are caused by that vaccination. Because there were no patterns among these reports, and since studies have not found ovarian failure to be associated with HPV vaccination, there is no evidence that would suggest that the Gardasil® vaccine caused the ovarian failure.
It is important to note that before Gardasil® was licensed, its safety was extensively studied in clinical trials [PDF - 4.9 MB]. These trials found no difference in amenorrhea (absence of a menstrual period in women of reproductive age) between recipients of Gardasil® [PDF - 355 KB] as compared to those receiving placebo (a harmless pill). Premature ovarian failure was not a noted outcome.
However, CDC continues to monitor closely for this condition following receipt of Gardasil®.
Some deaths have been reported to VAERS among persons who received HPV vaccine. Though a death might occur after a person receives a vaccine or medication, this does not mean that the vaccine or medication caused the death. All reports of death are reviewed by medical doctors at CDC or FDA.
Between June 2006 and March 2014, VAERS received 96 reports of death after people received the Gardasil® vaccine. CDC and FDA review all available information on reports of death following any vaccine, including Gardasil®. Among the 96 reports of death, many could not be verified, because there was not enough information reported; 47 could be verified through clinical review of medical records, autopsy reports, and death certificates. Detailed review of every report of death following a person’s receipt of the Gardasil® vaccine has shown:
- There is no pattern of death occurring with respect to time after vaccination
- There is no consistent vaccine dose number or combination of vaccines given
- There is no diagnosis at death that would suggest that the Gardasil® vaccine caused the death
Fainting, or syncope, is common after injections, especially among 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 you receive an injection of HPV vaccine or other vaccine.
Pain at the injection site, which resolves within a few days after injection, is one of the more frequently reported side effects of HPV vaccination. There have been a few reports in Japan of longer lasting pain, referred to as “complex regional pain syndrome” (an uncommon form of chronic pain that develops after an injury, surgery, stroke or heart attack, with pain out of proportion to the severity of the initial injury, if any), following HPV vaccination. In the United States, VAERS has received only 14 reports of chronic regional pain syndrome after HPV vaccination as of March 2014. In 10 of these reports, the symptoms began after vaccination. Because there was not a pattern among these reports, it is considered unlikely that chronic regional pain syndrome is a common risk after HPV vaccination. However, CDC continues to monitor closely the safety of all vaccines, including HPV.
Have FDA and CDC changed any recommendations for the use of HPV vaccines based on their vaccine safety monitoring?
Yes. When fainting (or syncope) was found to happen after vaccination, FDA changed Gardasil®’s prescribing information to include information about preventing falls and possible injuries from fainting after HPV vaccination. CDC consistently reminds doctors and nurses to share this information with all their patients.
CDC and FDA have reviewed all of the safety information available to them for both HPV vaccines and have determined that they are both safe. 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.
For additional information on HPV vaccines and CDC’s recommendations, please visit www.cdc.gov/HPV.
serious* - 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.