NAME: Vaccinia Virus
SYNONYM OR CROSS REFERENCE: Poxvirus, smallpox vaccine, VACV, VV
PATHOGENICITY/TOXICITY: VV normally has no serious health effects in humans, although it can cause disease of the skin when used to inoculate against the smallpox virus Footnote 1. Vaccinia virus is usually injected in the dermis where a localized lesion appears (a “take”), and then scabs over and heals in about 10-14 days Footnote 4. The vaccination is accompanied by fever, rash, lymphadenopathy, fatigue, myalgia and headaches in some patients Footnote 4, Footnote 5. Accidental infection with the virus can occur through contact between the vaccination lesion and broken skin (inadvertent inoculation) Footnote 6. Serious complications such as ocular vaccinia, myopericarditis, eczema vaccinatum (a papular, vesicular and pustular rash that is very infectious, 38 cases per million doses), progressive vaccinia (progressive necrosis at the vaccination site, 3 cases per million doses), postvaccinial CNS disease (headache, lethargy, seizures and coma, 12 cases per million doses), foetus malformations and abortion (very rare) sometimes occur after vaccination Footnote 5, Footnote 7, Footnote 8. Complications are more serious in immunosuppressed individuals and the smallpox vaccine usually causes one death for every million doses Footnote 5, Footnote 6. Contraindications to vaccine are their use in immunocompromised individuals, individuals with certain skin (e.g., eczema) and cardiac diseases, and pregnant women (Handley).
EPIDEMIOLOGY: Routine vaccination is not recommended due to the eradication of smallpox by 1980 Footnote 5, Footnote 9. US military and laboratory and health personnel working with the vaccine or other orthopox viruses still receive the vaccine Footnote 5.
INFECTIOUS DOSE: Unknown. Vaccine titre is usually 108 pock-forming units per ml Footnote 11.
MODE OF TRANSMISSION: The virus can be spread through the contact of a recently vaccinated individual with an unvaccinated person Footnote 9. Contact of a vaccinia virus lesion and broken skin is the most common mode of transmission between humans, although it has been shown that human-to-cattle and cattle-to-human transmission can occur, usually by touching the cow’s teats Footnote 9, Footnote 12.
INCUBATION PERIOD: As this is an immunizing agent, there is no incubation period; rather the time it takes to become immune is usually 7-14 days after vaccination Footnote 7.
COMMUNICABILITY: Vaccinia virus transmission between humans occurs through direct contact Footnote 9, Footnote 10. Vaccinee-to-cattle and cattle-to-human transmission has been shown, particularly due to contact with cow’s teats Footnote 9, Footnote 12.
RESERVOIR: Vaccinated humans.
ZOONOSIS: Occurs by contact with broken skin, from cattle to humans and vice-versa Footnote 12.
DRUG SUSCEPTIBILITY: None known
SUSCEPTIBILITY TO DISINFECTANTS: Susceptible to 0.02% sodium hypochlorite, 30% isopropanol, 40% ethanol, 0.02% glutaraldehyde, 0.01% benzalkonium chloride, 0.0075% iodine, 30% Sanytex and 0.12% ortho phenylphenol Footnote 13, Footnote 14. The virus is however resistant to solvent/detergent combinations (TNBP/Triton X-100 and TNBP/ Tween 80) and longer incubation periods (between 10 minutes and 24h depending on the solvent/detergent used) are necessary to inactivate the virus Footnote 15.
PHYSICAL INACTIVATION: The virus is inactivated by dry heat at 95 ºC for 2 hours Footnote 16. The heat-sensitive fraction of the virus is inactivated by moist heat at 60 ºC while the heat-resistant fraction may take higher temperatures to fully inactivate it Footnote 17. The virus in its aerosol form is also sensitive to UV light (254 nm) Footnote 18.
SURVIVAL OUTSIDE HOST: The dried virus can survive up to 39 weeks at 6.7% moisture and 4ºC Footnote 19.
Note: All diagnostic methods are not necessarily available in all countries.
FIRST AID/TREATMENT: Vaccinia immune globulin and cidofovir can be used to treat more serious complications such as eczema vaccinatum and progressive vaccinia Footnote 5. Supportive care should be given to patients with postvaccinial CNS disease Footnote 5.
IMMUNIZATION: A recent (10 years) smallpox vaccination is required for laboratory personnel working with the vaccinia virus (the smallpox vaccine and tissues, materials or animals that may be infected) or other orthopoxviruses because the virus can be spread to non-vaccinated individuals who are susceptible to complications Footnote 20.
LABORATORY-ACQUIRED INFECTIONS: 9 laboratory acquired infections were reported between 1986 and 2005 Footnote 2.
SOURCES/SPECIMENS: Lesion fluids or crusts, respiratory secretions and infected tissues containing the virus Footnote 20.
PRIMARY HAZARDS: Ingestion, parenteral inoculation, droplet or aerosol exposure to mucous membranes, and exposure to broken skin are the primary hazards when working with this agent Footnote 20.
SPECIAL HAZARDS: Certain poxviruses are stable at ambient temperature when dried Footnote 20.
RISK GROUP CLASSIFICATION: Risk group 2 Footnote 21.
CONTAINMENT REQUIREMENTS: Containment Level 2 facilities, equipment, and operational practices are recommended when working with the vaccine Footnote 20, Footnote 22. Viable materials should be manipulated in a biological safety cabinet Footnote 20.
PROTECTIVE CLOTHING: Lab coat. Gloves when direct skin contact with infected materials or animals is unavoidable. Eye protection must be used where there is a known or potential risk of exposure to splashes Footnote 22.
OTHER PRECAUTIONS: All procedures that may produce aerosols, or involve high concentrations or large volumes should be conducted in a biological safety cabinet (BSC). The use of needles, syringes, and other sharp objects should be strictly limited. Additional precautions should be considered with work involving animals or large scale activities Footnote 22. Laboratory personnel working with the agent should consider up-to-date vaccination Footnote 20.
SPILLS: Allow aerosols to settle and, wearing protective clothing, gently cover spill with paper towels and apply an appropriate disinfectant, starting at the perimeter and working towards the centre. Allow sufficient contact time before clean up.
DISPOSAL: Decontaminate all wastes that contain or have come in contact with the infectious organism by autoclave, chemical disinfection, gamma irradiation, or incineration before disposing.
STORAGE: The infectious agent should be stored in leak-proof containers that are appropriately labelled.
REGULATORY INFORMATION: The import, transport, and use of pathogens in Canada is regulated under many regulatory bodies, including the Public Health Agency of Canada, Health Canada, Canadian Food Inspection Agency, Environment Canada, and Transport Canada. Users are responsible for ensuring they are compliant with all relevant acts, regulations, guidelines, and standards.
UPDATED: December 2011
PREPARED BY: Pathogen Regulation Directorate, Public Health Agency of Canada.
Although the information, opinions and recommendations contained in this Pathogen Safety Data Sheet are compiled from sources believed to be reliable, we accept no responsibility for the accuracy, sufficiency, or reliability or for any loss or injury resulting from the use of the information. Newly discovered hazards are frequent and this information may not be completely up to date.
Public Health Agency of Canada, 2011