Contact transmission of vaccinia virus from smallpox vaccinees in the United States, 2003-2011.

Since 2002, approximately 40,000 US civilians and 2.1 million military personnel have been vaccinated against smallpox. The vaccine contains live vaccinia virus that can be transferred through physical contact. This report summarizes numbers, rates, and characteristics of contact vaccinia cases that presented between December 2002 and March 2011. Cases were identified from reports in adverse event reporting systems and peer-reviewed literature. One hundred fifteen cases of vaccinia transmission through contact were identified (5.4 per 100,000 vaccinees); 52 reports (45%) noted laboratory confirmation. Three-quarters of vaccinees, but fewer than 8% of contact vaccinia cases, were described as military members. Most cases were household or intimate contacts (n=86, 75%) or wrestling partners (n=18, 16%) of vaccinees. Nearly all cases manifested mild, local skin reactions; of 14 hospitalized cases, one was life-threatening. Vaccinia transmission from vaccinees is relatively infrequent. Continued attention to both vaccinee education and screening for contraindications to vaccination is appropriate.