Smallpox Vaccine


What is the smallpox vaccine and how does it work?

The smallpox vaccine was used until the early 1970s to wipe out smallpox worldwide. Much like other vaccines, the smallpox vaccine protects against infection by helping your body develop immunity to the smallpox virus. The smallpox vaccine is made from a live virus that’s very similar to the smallpox virus. The vaccine doesn’t cause smallpox, but it can cause life-threatening problems in some people (especially in people who have a weakened immune system).

Should everyone get the smallpox vaccine?

For most people, whether they are vaccinated against smallpox depends on whether there has been an outbreak of the disease. In most cases, the vaccine causes mild side effects, such as soreness around the vaccination site, fever, and body aches. A very small percentage of people will suffer serious side effects and may even die. Thus the vaccine is only necessary when there has been an outbreak of smallpox, or for a group of people who have been exposed to the virus. The following groups of people are more likely to have severe reactions and should only be vaccinated if actually exposed to smallpox:

  • Those who have a history of eczema or other chronic skin conditions, such as impetigo.
  • Those who have a condition that results in a weakened immune system, either naturally or because of treatment. This includes people who have cancer, HIV or AIDS, people who have recently had an organ transplant and people taking medicines such as steroids.
  • Those who are allergic to any ingredient in              the smallpox vaccine.
  • Those who are pregnant or nursing.
  • Children younger than 12 months of age.
  • Those who have a heart condition such as chest pain, history of heart attack or stroke, congestive heart failure or inflammation of the heart muscle (cardiomyopathy).
  • Those who have 3 or more of the following risk factors:
    • High blood cholesterol
    • High blood pressure
    • Diabetes or high blood sugar
    • A first degree relative (mother, father, brother or sister) who had a heart condition before 50 years of age
    • Currently smoke cigarettes
  • Those who share a household with someone who suffers from a skin condition or an immune system problem

I was vaccinated years ago—am I still protected?

Probably not. Studies show that the vaccine is most effective for 3 to 5 years after vaccination.


A note about vaccines

Sometimes the amount of a certain vaccine cannot keep up with the number of people who need it. More info...

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Written by editorial staff

Reviewed/Updated: 03/12
Created: 01/03