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Vaccine Adverse Event Reporting System plays vital role in safety :

July 21, 2016


Dr. MeissnerDr. MeissnerThe Vaccine Adverse Event Reporting System (VAERS) is a publicly accessible, national vaccine safety surveillance system conducted by the Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration. VAERS information is used to maintain vaccine safety and to reduce the rare side effects associated with vaccines. No active effort is made to collect information; rather data are received from those who voluntarily report their experience.


VAERS was established after Congress passed the National Childhood Vaccine Injury Act in 1986 requiring providers and vaccine manufacturers to report possible adverse events that occur during or following the administration of vaccines licensed in the United States. VAERS receives approximately 30,000 reports a year (Shimabukuro TT et al. Vaccine. 2015;30:4398). About 85% of VAERS reports describe mild adverse events such as fever or local reactions.

Which three of the following statements are true:

a) An adverse reaction is defined as any side effect, injury, toxicity or sensitivity reaction, or failure of pharmacologic action.

b) An adverse reaction occurring after vaccine administration does not need to be reported if it is considered to be unrelated to the vaccine.

c) Serious adverse events include death, life-threatening conditions, hospitalization, permanent disability, congenital anomaly or impairment of a body function. While these events may occur after vaccination, they rarely are caused by a vaccine.

d) Reports to VAERS are limited to reactions that follow routinely administered pediatric vaccines.

e) One function of VAERS is to detect adverse events that might be associated with a specific vaccine lot.

Answer: a, c and e are correct

Providers are required to report adverse events listed in the VAERS table of reportable events within a specified time following vaccine administration,

In addition, any adverse reaction listed by a vaccine manufacturer as a contraindication to further doses must be reported.

VAERS encourages the reporting of any clinically significant event even if the reporter is not certain the vaccine caused the event. Reporting applies to any vaccine licensed in the United States.

All VAERS reports are kept confidential as required by law. A patient’s consent is not required to release medical records to VAERS. In 2012, reports were received from health care providers (41%), manufacturers (29%), other sources (17%) and vaccinees or families (14%).

An advantage of VAERS is that reports are received from a variety of sources enabling rapid detection of rare adverse events. If a signal is detected, determination of whether a vaccine caused the reaction is not possible from VAERS data. A reported adverse event may be temporal (coincidental) or causal.

The lack of information regarding an unvaccinated comparison group precludes determination of the vaccine’s role. It is not possible to determine occurrence rates of a reported adverse event because it is not known how many people were vaccinated (denominator), how many vaccinated people did not experience an adverse event or how many unvaccinated people experienced the adverse event.

Another potential disadvantage of VAERS is reporting bias (such as underreporting) of an adverse event. The importance of VAERS is that a hypothesis can be generated and then tested in other surveillance programs.

Most common vaccine side effects are identified in clinical trials involving thousands of study participants before a vaccine is licensed. Post-licensure monitoring is essential because even large clinical trials may not identify rare side effects such as those that happen in one in 100,000 to one in 500,000 people. Second, vaccine trials may not include groups who might have different types of side effects or who might have a higher risk of side effects than participants in the clinical trials.

The CDC supports three additional programs that contribute to ongoing assessment of vaccine safety. The Vaccine Safety Datalink (VSD) is an active surveillance system that uses electronic health data from nine health care organizations (representing about 3% of the U.S. population) to address questions raised from VAERS reports or from the literature. The use of rapid cycle analysis allows VSD to evaluate the occurrence of adverse events in near-real time. Second, the Clinical Immunization Safety Assessment Project participates in identifying risk factors for adverse events, particularly in special populations. Third, the CDC's Immunization Safety Office has prepared for an emergency situation that requires mass immunizations in a short time period (such as during the National Smallpox Pre-event Vaccination Program).

VAERS objectives

Detect new or unusual vaccine adverse reactions

Monitor increases in known adverse events

Identify potential patient risk factors for particular adverse events

Identify specific vaccine lots associated with increased numbers or types of adverse events

Assess the safety of newly licensed vaccines

Dr. Meissner is professor of pediatrics at Floating Hospital for Children, Tufts Medical Center. He also is an ex officio member of the AAP Committee on Infectious Diseases and associate editor of the AAP Visual Red Book.

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