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The
Vaccine Adverse Event Reporting System (VAERS) is a national program administered by the
Food and Drug Administration (FDA) and
Centers for Disease Control and Prevention (CDC). VAERS monitors the safety of vaccines after they have been licensed and are in use in the community.
VAERS was established in 1990 after the National Childhood Vaccine Injury Act of 1986 mandated that physicians report certain vaccine adverse events to the Secretary of the Department of Health and Human Services. VAERS
provides a unified national system for reporting any possible
vaccine-related adverse events occurring after a U.S. licensed
vaccine has been received.
This is an important tool to ensure
vaccine safety by allowing the detection of early warning signs that new adverse events are related to vaccines or that known vaccine-related adverse events have changed in frequency. Even though all vaccines have been extensively studied in large numbers of individuals, some rare side effects may be seen only after the vaccine has been licensed and is in general use in the community. An example of this occurred after the rhesus rotavirus vaccine (Rotashield ®) was licensed in the 1990s. After widespread use of this vaccine, VAERS received reports of a higher than expected (more
than one per 10,000) number of cases of intussusception occurring soon after the first dose of vaccine was administered. These early reports led to withdrawal of the vaccine from the market and development of a new rotavirus vaccine that was recently introduced into the
childhood immunization schedule. This new rotavirus vaccine (RotaTeq®) was studied in
more than 70,000 children before it was licensed and the chance of developing intussusception was no different in children who received RotaTeq® and in children who received a placebo.
Who reports to VAERS?
Most reports to VAERS are voluntary. VAERS accepts voluntary reports from any individual who wants to report a possible adverse event that occurred after a vaccine was received. Examples of people who report such events are:
- Health care providers
- Parents
- Patients
- Anyone else
People are encouraged to report any adverse event, regardless of severity, that occurs after vaccination
even if they believe the vaccine was unlikely to be the cause.
Vaccine manufacturers are required to report all possible adverse events when they are made aware of them.
Strengths of VAERS
Ability to detect rare potential vaccine-related events in a timely fashion, thus ensuring that appropriate investigations and actions are quickly taken. Detects changes (either increases or decreases) in the incidence of known vaccine-related adverse events Easily accessible to the public and collects data from all persons, the only criteria being that the vaccination must precede the described adverse event Data collection is cost-effective Permits monitoring of the safety of specific vaccine lots Allows detection of individual
risk factors predisposing to vaccine adverse events. For example, advanced age was identified as a risk factor for illness after yellow
fever vaccine and syncope (fainting) after vaccine administration in adolescents and young adults. In response to the latter finding, a 15-minute waiting period after vaccination has been suggested.
Limitations of VAERS
Reports can be misrepresented as being proven vaccine-related adverse events.
A more correct interpretation is that VAERS reports serve as an alert system to generate hypotheses that certain events are vaccine-related and allow timely and definitive investigations occur Temporal rather than causal associations between vaccines and side-effects are detected Erroneous classification regarding severity. For example, any event that requires hospitalization no matter how straightforward and easily explained (for example, injection site problems) are automatically classified as “serious” whereas more biologically significant or unexpected problems that are treated in an outpatient setting do not meet the criteria for a serious adverse event Significant under-reporting occurs. It is estimated that the efficiency and completeness of reporting varies from lows of 1 percent for rashes after MMR vaccine to 72
percent for vaccine-associated poliomyelitis after receiving OPV. Highly susceptible to media reports. Reports of various side effects can increase many-fold after the condition has been highlighted in the print or audio-visual media Until recently, standardized case definitions for adverse events have not been available. Now the
Brighton Collaboration has been established to rectify this deficiency
 
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