VAERS: What we really know about the (m)
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|Mon, 03-17-2008 - 12:05pm|
March 5th, 2008
The Vaccine Adverse Event Reporting System (VAERS) is currently the only method of post-licensure surveillance for adverse reactions to vaccines in the United States. VAERS is a passive reporting system that allows physicians and parents to submit reports of potential adverse events post-vaccination. Unlike the mandatory reporting system for vaccine preventable diseases, there is no mandated system for the reporting of adverse events following vaccination. The FDA and CDC utilize VAERS for identifying adverse events associated with licensed vaccines (Chen, Rastogi, & Mullen, et al., 1994). Rosenthal and Chen (1995) note that vaccine trials “have sample sizes that are insufficient to detect rare adverse events” and “are usually carried out in well-defined, homogeneous populations with relatively short follow-up periods which may limit their generalizability (p.1706)”. Therefore, it can be assumed that accurate reporting of adverse events to VAERS is a critical issue in indentifying adverse events that occur in the general population. Unfortunately, current literature suggests that VAERS is, at best, poorly utilized (Rosenthal & Chen, 1995).
A 2007 study by Heinrichsen, Kruskal, O’Brien, Lieu, and Platt found that when physicians were prompted by their computer based medical records system they reported 6 times (.69 per 1000 vs. 0.11 per 1000) the amount of adverse events traditionally reported to VAERS. Let’s take a closer look at this study:
“During 5 months, a total of 33,420 vaccinations were administered during 14,466 encounters. There were 5,914 follow-up contacts by vaccinees within 14 days of the vaccination visits; 686 (11.6%) generated an alert. Clinicians submitted VAERS reports for 23 of these (0.69 per 1000 vaccines doses), which is almost 6 times the dose-based reporting rate to VAERS (p.731).”
The interesting observation here is that while 686 alerts for potential adverse events were generated, only 23 reports to VAERS resulted from these alerts. It is likely that some of the alerts were not reported because they were viewed as not being adverse events by the attending physicians. Regardless, it also seems unlikely that only 23 adverse events actually occurred among the 686 flagged events. Just for fun, let’s see what that number would look like. This study found a 0.69 per 1000 rate of adverse events. But using the number of flagged events instead of the number of actually reported events, we arrive at a 21 per 1000 rate of potential adverse events. These 23 adverse events represent only 3.3% of the potential events. Unfortunately, the authors of this study did not feel that this merited discussion so it is impossible to determine how many adverse events actually occurred in relation to how many were reported.
After the study period had completed, the study authors sent surveys to the participating pediatric providers. The results of this survey were alarming: Out of the 101 pediatric providers who received an alert about a potential adverse event, only 12% felt that “any of the alerts corresponded to an actual vaccine side effect (p.733)”. Another concerning finding was that, “The most common reasons cited for not completing the questions were that the clinicians thought it was unnecessary and that they were too busy (p.733).” Finally, the study found that 50% of pediatric providers who submitted a report to VAERS during the study said that they had never before reported an adverse event to VAERS. This data suggests that not only are doctors failing to report adverse events to VAERS, but that the prevailing attitude is that adverse events simply do not occur. Without a willingness to recognize and report adverse events, a passive surveillance system such as VAERS cannot be relied upon to accurately reflect the adverse events that do occur.
Is anyone else concerned that the CDC and FDA rely on this type of flawed reporting system to determine post-licensure adverse events following vaccination? What are the actual rates of adverse events following vaccination? Unfortunately, it seems like no one has an accurate answer to this question. And no one seems interested in finding out.
Hinrichsen, V.L., Kruskal, B., O’Brien, M.A., Lieu, T.A., Platt, R. (2007). Using electronic medical records to enhance detection and reporting of vaccine adverse events. Journal of the American Medical Informatics Association, 14, 731-735.