Smallpox Vaccine and Cancer

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What if a person is exposed to the smallpox virus?

Smallpox is not transmitted by insects or animals. The chance of anyone being exposed to smallpox is very small, since the only known sources are isolated labs. Though there’s no treatment, it is known that giving a person the vaccine even a short time after exposure (within 3 days) gives some protection against smallpox.

For some people with cancer, if they are actually exposed to smallpox, the risk of having smallpox may be higher than the risks linked to getting the vaccine. In the past, about 1 in 3 people with smallpox died, so the disease itself can be deadly. In cases like this, vaccinating after exposure can help.

Even so, there are some people who still may not be able to get vaccinated even if they have been exposed to smallpox. Anyone who has a reason to get the smallpox vaccine should first discuss the risks and benefits with a doctor.

You can find the CDC’s information about smallpox, the vaccine, and their smallpox outbreak plan on their website at or call them at 1-800-CDC-INFO (1-800-232-4636) or TTY 1-888-232-6348.

Last Medical Review: 02/24/2014
Last Revised: 02/24/2014