(HealthDay News) – The potential exists for further transmission of vaccinia virus beyond the direct sexual contacts of smallpox vaccinees, according to a case report published in the March 1 issue of the U.S. Centers for Disease Control and Prevention’s Morbidity & Mortality Weekly Report.

Hai Shao, MD, PhD, from the Scripps Mercy Hospital in San Diego, and colleagues describe the epidemiology and clinical course of the secondary and tertiary cases and efforts to prevent further transmission to contacts.

The researchers say that the smallpox vaccine had been administered under the U.S. Department of Defense smallpox vaccination program. While the vaccinee did not experience vaccine-associated complications, a male with whom he had sexual intercourse with presented with a painful perianal rash and a lesion on his upper lip, as well as fever, malaise, nausea and vomiting, and a history of eczema, which can be a risk factor for adverse reactions to vaccinia infection. The patient with secondary infection reported sexual intercourse with another male partner, following presentation of his rash but prior to his hospitalization. This male, too, sought medical attention (two days following intercourse) for malaise as well as papular penile lesions and a lesion on his forearm. Both patients were hospitalized and received vaccinia immune globulin intravenous. Their lesions healed without complications.

“This case report is the first reported instance of tertiary vaccinia transmission through sexual contact,” the authors write.

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