Questions & Answers
Smallpox - Vaccine Safety
Back to Parent Q&A Category Back to All Smallpox Q&A Back to All Q&A Back to Smallpox


  1. Is smallpox vaccine safe?
    The smallpox vaccine is the best protection you can get if you are exposed to the smallpox virus. Most people experience mild, reactions, such as sore arm, fever, headache, body ache, and fatigue. These symptoms may peak 8 to 12 days after vaccination.

  2. Why should I take this vaccine?

    People in many countries are concerned about the potential use of smallpox as a bioterrorism agent. The U.S. government has been preparing for some time for the remote possibility of an outbreak of smallpox as an act of terror. Those preparations quickened after September 11, 2001.

    The likelihood that smallpox would be used as a bioweapon is unknown. About 30 percent of people who contract smallpox die; about 70% survive.

    Vaccination prevents almost all cases of smallpox. If symptoms of smallpox do appear, they are generally milder than in unvaccinated people.

  3. What are the temporary side effects after smallpox vaccination?

    Mild reactions include swelling and tender lymph nodes that can last two to four weeks after the blister heals. Most people develop itching, headache, fatigue, muscle aches, pain, or chills after smallpox vaccination, usually about eight to 12 days later. Some individuals may have rashes that last two to four days. These side effects are usually temporary and self-limiting, meaning they go away on their own or with minimal medical treatment, for example aspirin and rest.

    If the vaccination is successful, a red and itchy bump develops at the vaccine site in three or four days. Then, in the first week, the bump becomes a large blister and fills with pus. During the second week, the blister begins to dry up and a scab forms. The scab falls off in the third or fourth week, leaving a small scar. People who are being vaccinated for the first time have a stronger reaction than those who are being revaccinated.

    If someone does not get the expected vaccination site response, they need to be revaccinated. If someone has a question or concern about the smallpox vaccination site they should contact their primary-care manager, medical department representative or their healthcare provider.

  4. Is it okay to take multiple vaccines at the same time?
    Multiple inoculations do not weaken or overwhelm the immune system. The immune system has an enormous capacity to respond to immune stimuli from vaccines. Far from weakening an immune system, vaccines actually strengthen the body's natural defenses against serious and potentially fatal infections. Even infants are capable of generating protective immune responses to multiple vaccines given at the same time.

  5. Can someone vaccinated against smallpox infect someone else?
    Yes. However, infection of this kind can be prevented with covering the site and frequent hand washing. Adverse reactions, sometimes severe, can also occur in people who come in contact with a vaccinated person. These problems result from touching the vaccination site and transferring the vaccine virus to another person.

  6. Is it safe to have surgery soon after I get the smallpox vaccine?
    If you must have surgery, inform your surgeon that you have just received smallpox vaccine. Elective or nonurgent surgery is not recommended within 30 days after smallpox vaccination. This allows time for the vaccination site to heal completely, so that it cannot spread smallpox vaccine virus to your surgical wound. Eye surgery, for example Lasik eye surgery, is a special contraindication to receiving smallpox vaccine. Eye surgery should be delayed until after the smallpox vaccination site has healed completely. Please contact the IHB if you have questions or concerns.

  7. Is it safe to go swimming after my smallpox vaccination?
    Do not swim in pools, hot tubs or whirlpools until your smallpox vaccination site has healed. There is a theoretical risk of spreading the virus to others. Also, the chemicals used in pool water could make your vaccination less effective.

  8. Can I get smallpox disease from smallpox vaccine?
    The smallpox vaccine is made from vaccinia virus, which is a live virus similar to smallpox virus. Vaccinia virus cannot cause smallpox disease.

  9. What laboratory tests should I order if I suspect a contact transmission of the vaccinia virus?
    Identify infectious agents through scraping or aspiration of lesion content: herpes simplex (HSV) and varicella are most common etiologies and can be rapidly assessed with DFA (direct fluorescent antibody screening slide) followed by culture. These diagnoses are more common than vaccinia. Bacterial cultures may be indicated. If DFA is negative for HSV, varicella, then obtain vaccinia PCR and culture.