Vaccinia Virus (Cow Pox)

Prepared by: Michael J. Huerkamp, DVM, Diplomate ACLAM
Date: July 3, 2000

Agent: Vaccinia Virus (Cow Pox)

Vaccinia is the virus strain used to immunize humans against smallpox (variola). Many DAR employees, especially those born before 1971, may have been given a vaccine with this agent in childhood.

Potential Hazard: Experimentally infected animals are potentially source of infection for non-immunized personnel. Poxvirus may be present in lesions or crusts, respiratory secretions, or tissues of infected animals. Transmission of the virus can occur by inhalation, ingestion or inoculation of the mucous membranes or broken skin. Skin rash and fever of one day duration occurs in the case of uncomplicated infection. Brain infection is rare. Immunosuppressed individuals (i.e., those infected with the AIDS virus or being treated for cancer) are at risk of more severe infection and even death with progressive vaccinia infection.

Recommended Precautions: The animal biosafety level II practices (DAR SOP 400-3) will protect husbandry personnel against exposure or infection. Individuals working with vaccinia should be immunized. Adult Americans born before 1971 are or should have been immunized with vaccinia as infants and may be immune to infection, but researchers, veterinarians, and animal care technicians working with or potentially exposed to infected animals should consider re-vaccination every 10 years. Vaccination is available to DAR employees; those declining vaccination or revaccination must sign a declination form. Fever and a pustule at the vaccination site are common side effects of vaccination.

References:Biosafety in Microbiological and Biomedical Laboratories, 4th edition, CDC-NIH, 1999, pp. 166-7. Henderson D. A. Smallpox: Clinical and epidemiologic features. Emerging Infec Dis 5(4), 1999. MMWR. December 13, 1991/40(RR14); 1-10