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SMALLPOX SUPPLEMENTAL FACT SHEET

Investigational Vistide® (Cidofovir) Information

The smallpox vaccine is made from a live virus related to smallpox called vaccinia. The vaccine stimulates the immune system to react against the vaccinia virus, and develop immunity to it. Immunity to vaccinia also provides immunity to smallpox. For most people, live virus vaccines are safe and effective. Some people, however, are at greater risk for serious side effects from the smallpox vaccine.

Vistide (cidofovir), a drug licensed to treat serious viral infections of the eye in HIV-infected people, may help people who have certain serious reactions to the smallpox vaccine. If you develop a serious reaction to the smallpox vaccine, and VIG (another medicine used to treat bad reactions to the smallpox vaccine) is not available or is not working, you may be offered cidofovir. While this drug has not been used to treat patients with bad reactions to smallpox vaccine, early results from laboratory studies suggest that cidofovir may work against the vaccinia virus. Use of cidofovir would be administered under an Investigational New Drug (IND) protocol.

Cidofovir Information:

  • Vistide® (Cidofovir) is licensed to treat cytomegalvirus (CMV) retinitis (a serious eye infection) in HIV-infected people. It is not licensed to treat the problems caused by smallpox vaccine so it can only be used 'off-label' (prescribed by a physician to treat a condition for which it has not been specifically approved) or through a special protocol called an Investigational New Drug (IND) protocol.
  • Use of cidofovir to treat smallpox vaccine reactions should be evaluated and monitored by experts at the National Institutes of Health and the Centers for Disease Control and Prevention.
  • Cidofovir might be used to treat individuals who have developed generalized vaccinia, eczema vaccinatum, or progressive vaccinia after receiving the smallpox vaccine.

How is cidofovir administered?

Cidofovir is injected through a needle in the vein. Fluids will be given through the vein and another medication (probenecid) given by mouth both before and after cidofovir. These may help decrease the side effects of cidofovir.

Side Effects:

  • Kidney problems that can lead to kidney failure.
  • Low white blood cells.
  • Pressure in the eye.
  • Swelling and tenderness of the eye.
  • Build up of acid in the body that can result in liver problems and inflammation of the pancreas that can result in death.
  • Other problems include fever, infection, pneumonia, shortness of breath and nausea with vomiting.
  • Cidofovir can cause headache, weakness, rash, hair loss, diarrhea, pain, lowered number of red blood cells, loss of appetite, chills, coughing, and infections in the mouth.
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