OBJECTIVE: In March 2018, the US Department of Defense (DOD) added the smallpox vaccination, using ACAM2000, to its routine immunizations, increasing the number of persons receiving the vaccine. The following month, Fort Hood reported a cluster of 5 myopericarditis cases. The Centers for Disease Control and Prevention and the DOD launched an investigation. METHODS: The investigation consisted of a review of medical records, establishment of case definitions, causality assessment, patient interviews, and active surveillance. A 2-sided exact rate ratio test was used to compare myopericarditis incidence rates. RESULTS: This investigation identified 4 cases of probable myopericarditis and 1 case of suspected myopericarditis. No alternative etiology was identified as a cause. No additional cases were identified. There was no statistically significant difference in incidence rates between the observed cluster (5.23 per 1000 vaccinated individuals, 95% CI: 1.7-12.2) and the ACAM2000 clinical trial outcomes for symptomatic persons, which was 2.29 per 1000 vaccinated individuals (95% CI: 0.3-8.3). CONCLUSIONS: Vaccination with ACAM2000 is the presumptive cause of this cluster. Caution should be exercised before considering vaccination campaigns for smallpox given the clinical morbidity and costs incurred by a case of myopericarditis. Risk of myopericarditis should be carefully weighed with risk of exposure to smallpox.

Although canine rabies virus variant (CRVV) was successfully eliminated from the United States after approximately 6 decades of vaccination campaigns, licensing requirements, and stray animal control, dogs remain the principal source of human rabies infections worldwide. A rabies vaccination certificate is required for dogs entering the United States from approximately 100 countries with endemic CRVV, including Egypt (1). On February 25, 2019, rabies was diagnosed in a dog imported from Egypt, representing the third canine rabies case imported from Egypt in 4 years (2,3). This dog and 25 others were imported by a pet rescue organization in the Kansas City metropolitan area on January 29. Upon entry into the United States, all 26 dogs had certificates of veterinary inspection, rabies vaccination certificates, and documentation of serologic conversion from a government-affiliated rabies laboratory in Egypt. CDC confirmed that the dog was infected with a CRVV that circulates in Egypt, underscoring the continued risk for CRVV reintroduction and concern regarding the legitimacy of vaccine documentation of dogs imported from countries considered at high risk for CRVV. Vaccination documentation of dogs imported from these countries should be critically evaluated before entry into the United States is permitted, and public health should be consulted upon suspicion of questionable documents.