Smallpox vaccine postexposure

Smallpox vaccine is not recommended for use in certain groups who may be at risk for complications of the vaccine, in up to 0.2% or more of immunized populations, immunosuppressed individuals, pregnant women, and patients with atopic dermatitis may develop complications related to vaccinia, the orthopox virus used in smallpox vaccine. Vaccinia immunoglobulin can be given to those at risk for these complications. Smallpox vaccine can also be given up to 4 days postexposure as postexposure prophylaxis with significant reduction in mortality. 

Smallpox vaccination is also effective if given after exposure to the disease. Studies of household contacts in India and Pakistan revealed that postexposure vaccination reduced secondary cases up to 91%. The lowest secondary attack rates occurred in contacts vaccinated less than seven days after exposure. Smallpox cases that occurred were typically less severe (modified smallpox) in household contacts receiving postexposure vaccination (25). 

D. Vaccine/Prophylaxis. Smallpox vaccine (vaccinia virus) is a licensed live poxvirus vaccine that induces strong cross-protection against smallpox. Reliable data are sparse as to efficacy and durability of protection. The duration vaccinia induced immunity is at least 3 years. Vaccine immunity may prevent or modify illness. Fully immune individuals exposed to the virus by the respiratory route may develop fever, sore throat, and conjunctivitis ("contact fever") lasting several days. The vaccine is administered by dermal scarification or intradermal jet injection. The appearance of a vesicle or pustule within several days indicates that the vaccine will be effective. Other available countermeasures include the postexposure use of Vaccinia immune globulin or primary vaccination within 3-4 days of exposure yields some protection. 

Vaccines. Anthrax and smallpox vaccines can be used before exposure and also for postexposuie prophylaxis. A pentavalent (ABODE) botulinum toxoid is currently used for laboratory workers at high risk of exposure. It is not effective for postexposure prophylaxis. Vaccines are not currently available for plague, tularemia, or viral hemorrhagic fevers. 

After an aerosol release of smallpox, public health authorities will make vaccine supplies available to affected communities. Postexposure vaccination is effective in preventing infection or lowering mortality up to 4 days after exposure. Physicians should give the vaccine to suspected cases to ensure that a mistaken diagnosis does not place patients at risk for smallpox. An emergency vaccination program should also include (26) ... 

Evidence indicates that vaccinia-immune globulin is of value in postexposure prophylaxis of smallpox when given (a) within the first week following exposure and (b) concurrently with vaccination.121 However, the prophylactic use of VIG should be carefully weighed vis-a-vis the risk of attenuating the immune response to booster vaccination. 

Vaccinia vaccine remains the preeminent countermeasure for preexposure prophylaxis against smallpox. Vaccinia vaccination, vaccinia immune globulin, and methisazone each possess some efficacy in postexposure prophylaxis. 

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