Under-reporting of Adverse Events
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|Wed, 12-10-2008 - 11:54am|
The Clinical Impact of Adverse Event Reporting
Another major concern with any spontaneous reporting system is underreporting of adverse events (16, 30-32). It has been estimated that rarely more than 10% of serious ADRs, and 2-4% of non-serious reactions, are reported to the British spontaneous reporting program (30). A similar estimate is that the FDA receives by direct report less than 1% of suspected serious ADRs(32). This means that cases spontaneously reported to any surveillance program, which comprise the numerator, generally represent only a small portion of the number that have actually occurred. The effect of underreporting can be somewhat lessened if submitted reports, irrespective of number, are of high quality.
(16) Chen RT, Rastogi SC, Mullen JR, Hayes SW, Cochi SL, Donlon JA, et al. The Vaccine Adverse Event Reporting System (VAERS). Vaccine 1994;12:542-550
(30) Rawlins MD. Pharmacovigilance: paradise lost, regained or postponed? The William Withering Lecture 1994. J R Coll Physicians Lond 1995;29:41-49
(31) Strom BL, Tugwell P. Pharmacoepidemiology: current status, prospects, and problems. Ann Intern Med 1990;113:179-181
(32) Scott HD, Rosenbaum SE, Waters WJ, Colt AM, Andrews LG, Juergens JP, et al. Rhode Island physicians' recognition and reporting of adverse drug reactions. R I Med J 1987;70:311-316
Vaccine Adverse Event Reporting System (VAERS): Usefulness and Limitations
by M. Miles Braun, MD MPH
Underreporting is an inherent problem of passive surveillance systems, including VAERS. The degree of underreporting varies according to the adverse event. For example, one study estimated that 68% of cases of vaccine-associated polio are reported to VAERS, but only 4% of MMR-associated thrombocytopenia are reported (9). This variability in undereporting can make it hazardous to assume that the relative frequencies of adverse events in VAERS reflects their relative rates of occurrence. In addition, for new products on the market, increased reporting of adverse events may occur; this has been termed the "Weber effect" (10).
(9) Rosenthal S, Chen R. The reporting sensitivities of two passive surveillance systems for vaccine adverse events. Am J Public Health 1995;85:1706-9.
(10) Weber JCP. Epidemiology of adverse reactions to non-steroidal antiinflammatory drugs. Advances in Inflammation Research 1984;6:1-7.