Smallpox Vaccine

What Is Smallpox?

Smallpox is a disease caused by a virus. It spreads easily and can be deadly. Worldwide vaccines have stopped smallpox.

Governments have studied smallpox as a germ-warfare weapon. As a weapon, it would be released in the air. Those exposed could develop the disease. They would then pass it to other people.

Smallpox can be spread by direct, face-to-face contact. It can also be spread through body fluids, linens, and clothing that contains the virus. Smallpox can be spread through the air, but this is rare.

Symptoms may include:

  • High fever
  • Headache
  • Body aches
  • Vomiting

As the illness goes on, a red rash appears on the tongue and in the mouth. The rash then spreads. Spots begin to break open. The red spots turn into raised bumps. By day 4, the bumps fill with fluid. Scabs form over all the bumps.

What Is the Smallpox Vaccine?

The smallpox vaccine contains a live virus. It is related to smallpox. The vaccine is usually given in the arm as pinpricks.

Who Should Get Vaccinated and When?

The vaccine is not given to most people. It is given to those at risk. This includes the military and those who work in high threat areas.

What Are the Risks Associated With the Smallpox Vaccine?

A live virus is injected into the skin. It is possible to spread it to other areas of the body, or even to other people. To prevent this from happening, the injection site must be protected.

Common side effects of the smallpox vaccine include:

  • Rash and itching
  • Fever
  • Headache
  • Tiredness
  • Swollen lymph nodes
  • Body aches
  • Soreness in the arm

More serious, but less common side effects include:

  • Inflammation of the heart muscle or sac around the heart
  • Swelling of the brain or spinal cord
  • Infection at the site of the vaccine
  • Severe allergic reaction

Who Should Not Get Vaccinated?

The vaccine is not advised for:

  • Anyone with a past allergic reaction to the vaccine or any of its parts
  • Pregnant or breastfeeding women
  • Children less than 12 months old
  • People with eczema or certain other skin conditions
  • People with heart conditions, a high risk for heart disease, or stroke -like symptoms
  • People with weakened immune systems from certain conditions or medicines

Talk to your doctor to find out if the vaccine is safe for you.

What Happens in the Event of an Outbreak?

If an outbreak happens, the US has a large supply of the smallpox vaccine. People would get the vaccine.

Centers for Disease Control and Prevention
Department of Health & Human Services


Emergency preparedness for vaccine safety. Centers for Disease Control and Prevention website. Available at: Accessed August 24, 2021.
Meyer H, Ehmann R, et al. Smallpox in the post-eradication era. Viruses. 2020 Jan;12(2):138.
Smallpox. Centers for Disease Control and Prevention website. Available at: . Accessed August 24, 2021.
Smallpox. EBSCO DynaMed website. Available at: Accessed August 24, 2021.
Last reviewed July 2021 by EBSCO Medical Review Board David L. Horn, MD, FACP
Last Updated: 8/24/2021

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