Prevention and Treatment

There are vaccines to protect people from smallpox. Currently, the smallpox vaccine is not recommended for the general public because smallpox has been eradicated. If there were a smallpox outbreak, health officials would use a smallpox vaccine to control it. While some antiviral drugs may help treat smallpox disease, there is no treatment for smallpox that has been tested in people who are sick with the disease and proven effective.

Smallpox Vaccine

Smallpox can be prevented by the smallpox vaccine, also called vaccinia virus vaccine. The vaccine is made from a virus called vaccinia, which is a poxvirus similar to smallpox, but less harmful. There are two licensed smallpox vaccines in the United States and one investigational vaccine that may be used in a smallpox emergency.

The replication-competent smallpox vaccines (i.e., ACAM2000 and APSV) can protect people from getting sick or make the disease less severe if they receive the vaccine either before or within a week of coming in contact with smallpox virus. If you get the vaccine:

  • Before contact with the virus, the vaccine can protect you from getting sick.
  • Within 3 days of being exposed to the virus, the vaccine might protect you from getting the disease. If you still get the disease, you might get much less sick than an unvaccinated person would.
  • Within 4 to 7 days of being exposed to the virus, the vaccine likely gives you some protection from the disease. If you still get the disease, you might not get as sick as an unvaccinated person would.

Once you have developed the smallpox rash, the vaccine will not protect you.

Currently, the smallpox vaccine is not available to the general public because smallpox has been eradicated, and the virus no longer exists in nature. However, there is enough smallpox vaccine to vaccinate every person in the United States if a smallpox outbreak were to occur.

For more details about the vaccine, see Smallpox Vaccine Basics.

Antiviral Drugs

  • In July 2018, the FDA approved tecovirimat (TPOXX) for treatment of smallpox. In laboratory tests, tecovirimat has been shown to stop the growth of the virus that causes smallpox and to be effective in treating animals that had diseases similar to smallpox. Tecovirimat has not been tested in people who are sick with smallpox, but it has been given to healthy people. Test results in healthy people showed that it is safe and causes only minor side effects. In addition to treating smallpox disease, tecovirimat could also be used under an investigational new drug (IND) protocol to treat adverse reactions from vaccinia vaccination.
  • In laboratory tests, cidofovir and brincidofovir have also been shown to stop the growth of the virus that causes smallpox and to be effective in treating animals that had diseases similar to smallpox. Cidofovir and brincidofovir have not been tested in people who are sick with smallpox, but they have been tested in healthy people and in those with other viral illnesses. These drugs continue to be evaluated for effectiveness and toxicity. Neither are FDA-approved for the treatment of variola virus infections (secondary to smallpox vaccination), but they could be used for isolated cases or during an outbreak under an appropriate regulatory mechanism (such as an investigational new drug [IND] protocol or Emergency Use Authorization) for the treatment of complications from vaccinia vaccination.

Because these drugs were not tested in people sick with smallpox, it is not known if a person with smallpox would benefit from treatment with them. However, their use may be considered if there is ever a smallpox outbreak.

Tecovirimat and cidofovir are currently stockpiled by the Assistant Secretary for Preparedness and Response (ASPRexternal icon) Strategic National Stockpileexternal icon, which has medicine and medical supplies to protect the American public if there is a public health emergency, including one involving smallpox.

Antiviral Drugs for the Treatment of Smallpox Disease
Drug FDA approved for smallpox treatment? Available through IND protocol for smallpox treatment? Available in Strategic National Stockpile?
Tecovirimat Yes Not applicable Yes
Cidofovir No Yes Yes
Brincidofovir No No No