Ischemic cardiac events and other adverse events following ACAM2000® smallpox vaccine in the Vaccine Adverse Event Reporting System

Background: The Vaccine Adverse Event Reporting System (VAERS) is a passive reporting system, used for monitoring the safety of all US licensed vaccines. In March 2008, ACAM2000 (R) replaced Dryvax (R) as the only licensed smallpox vaccine and is administered to all persons entering military service and certain civilian researchers. In 2011, routine data mining of VAERS identified a vaccine safety concern resulting in acute ischemic cardiac events (ICE) following ACAM2000 (R). Methods: During March 1, 2008 through June 30, 2013, we reviewed all serious reports received following ACAM2000 (R) and classified them by diagnostic category. We identified possible ICE cases by searching the Medical Dictionary for Regulatory Affairs (MedDRA (R)) terms for "myocardial ischaemia," "acute myocardial infarction," "myocardial infarction," and "ischaemia," and applied standardized surveillance case definitions. Results: VAERS received 1149 reports following ACAM2000 (R) administration; 169 (14.7%) were serious (resulting in permanent disability, hospitalization or prolongation of hospitalization, life-threatening illness or death), including one death. The two most frequent diagnostic categories for serious reports were cardiovascular and other infectious conditions. The MedDRA (R) search found 31 reports of possible ICE after receipt of ACAM2000 (R) vaccine. Of a total 30 possible ICE cases with demographic information, all but one was male; the age range was 20-45 years (median 32) and median interval to onset of symptoms was 12 days. On clinical review there were 16 cases of myocarditis/pericarditis and 15 ICE cases. Conclusions: Our review of the data mining signal did not substantiate the concerns about ICE after ACAM2000 (R). Our study also suggests that with current pre-vaccination screening, cardiac morbidity in generally healthy vaccinated populations remains uncommon. Published by Elsevier Ltd.