Editor’s note: This is the second VaccineSmarts article in a two-part series about vaccine safety. A reader asked how we know that vaccines are safe. The first column discussed safety testing during clinical trials and standards for vaccine manufacturing.

The Centers for Disease Prevention and Control has a series of programs to detect safety issues that may occur once a vaccine has been approved. The Vaccine Adverse Event Reporting System is an early warning system. It depends on the public to report adverse events following vaccination.

Anyone can file a VAERS report, including health care providers, vaccine recipients or their family members and manufacturers. The CDC investigates the serious reports. The reports may suggest a safety issue with a vaccine but do not prove it. In other words, just because something bad happens following vaccination does not mean the vaccine caused it.

The reports are stripped of all personal identifying information and are available to the public. Concerns generated by the VAERS data prompts the Food and Drug Administration and CDC to investigate further.

The second program is the Vaccine Safety Datalink. This program is a collaborative effort among the CDC and several large health care organizations such as Kaiser Permanente, Group Health Cooperative and Harvard Pilgrim. The VSD utilizes the de-identified data from the more than seven million patients that are members of these organizations.

Safety issues can be quickly identified as the data is updated weekly. The VSD program can analyze the data in a number of ways. For example, the program compares adverse events occurring in vaccinated and unvaccinated members. VSD also can look at the timing of adverse events in relation to vaccination. Data from the program are also available to researchers not associated with the government.

The third part of the CDC program is known as the Clinical Immunization Safety Assessment Project. This program is headed by a group of vaccine safety experts from the CDC and seven medical research centers such as Columbia University, Duke University and Johns Hopkins University.

CISA looks at issues that arise from VAERS, VSD and other sources, and provides expert advice. They develop research studies that address priorities such as influenza vaccine safety and vaccine safety in pregnant women.

Finally, many others are on the lookout for safety issues. Manufacturers are required to collect information about adverse events and report them to the government. Independent researchers perform and publish numerous studies on vaccine safety that should reassure those who are distrustful of the government. The risks associated with vaccines are very small compared to the risks associated with the diseases that vaccines prevent.

With advances in genomics and personalized medicine, vaccines may become even safer in the future. Presently, vaccine testing, manufacturing standards and safety monitoring keeps vaccines as safe as the limits of our science allow.

Dr. Richard Rupp is a pediatrician and professor and Bridget Hawkins is an assistant professor of anesthesiology. They are both members of UTMB’s Sealy Center for Vaccine Development. This column is meant to provide educational information about vaccines. Visit our new blog at blogs.utmb.edu/vaccinesmarts/ or like us on Facebook, or follow us on Twitter @VaccineSmarts.