Vaccinia vaccine is used to immunise against smallpox, which is caused by the orthopoxvirus, variola. A 26-year-old laboratory worker was inoculating mice with vaccinia vaccine as part of research into cross-reactivity among poxviruses. This particular vaccine contained a live attenuated strain of vaccinia (Western Reserve). The laboratory worker had himself received vaccinia vaccine in 2004 because of the nature of his work. On this occasion, after inoculating two mice, he suffered a needlestick injury to the left index finger.

Two days later, a cloudy vesicle, typical of vaccinia virus,1 appeared at the inoculation site (Figure, arrow). After 3 more days, the finger became acutely inflamed, with secondary lymphangitis and axillary lymphadenitis. After antibacterial therapy, the lymphangitis and lymphadenitis rapidly resolved and the vesicle disappeared within 10 days. The man remains well.

Infection with vaccinia usually follows vaccination or needlestick injuries. Although this is usually mild and self-limiting, certain conditions (eg, immunocompromise, pregnancy, eczema) predispose to more severe and even fatal illness. Prior immunisation with the vaccinia vaccine is thought to prevent or reduce the severity of such infections, and it is recommended that people working with vaccinia or related orthopoxviruses be vaccinated every 10 years.1 Vaccinia immunoglobulin and certain antiviral agents have been used to treat severe infections.2

Given the potential dangers from accidental exposure and the fact that the last documented case of smallpox (in 1978) was related to a laboratory incident,3 strict infection control measures are paramount, including disinfection after injury, prompt reporting, urgent medical review, and measures to minimise secondary spread to contacts.1