VAERS data cannot be used to prove a causal association between the vaccine and the adverse event. The only association between the adverse event and vaccination is temporal, meaning that the adverse event occurred sometime after vaccination. Therefore, the adverse event may be coincidental or it may have been caused by vaccination, however we cannot make any conclusions that the events reported to VAERS were caused by the vaccine.
HPV Vaccine Safety
There are two licensed HPV vaccines, Gardasil® and Cervarix®, available to protect against the types of HPV infection that cause most cervical cancers. Gardasil® was licensed for use in females, age 9-26 years in June 2006 and for males age 9-26 years in Oct 2009. Cervarix® was licensed for use in females age 10-25 in October 2009.
The safety of HPV vaccines was studied in clinical trials worldwide before licensure. For Gardasil® , over 29,000 males and females participated in these trials. For Cervarix®, over 30,000 females participated in several clinical trials.
Since licensure, CDC and FDA have been closely monitoring the safety of HPV vaccines. There are 3 systems used to monitor the safety of vaccines after they are licensed and used in the U.S. These systems can monitor adverse events already known to be caused by vaccines, as well as detect rare adverse events that were not identified during pre-licensure clinical trials. The 3 systems are:
- The Vaccine Adverse Event Reporting System (VAERS)–a useful early warning public health system that helps CDC and FDA detect possible side effects or adverse events following vaccination.
- The Vaccine Safety Datalink (VSD) Project–a collaboration between CDC and 10 health care organizations which monitors and evaluates adverse events following vaccination.
- The Clinical Immunization Safety Assessment (CISA) Network– a collaboration between6 academic centers in the U.S. which conduct research on adverse events that might be caused by vaccines.