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smallpox overview

Last Updated:
21 May 15

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  arrow Vaccination Site Care
Normal Responses Adverse Reactions

Normal Responses

General Normal Responses
Most people experience normal, usually mild, side effects, such as swollen lymph nodes, sore arm, fever, headache, body ache, and fatigue. These symptoms may peak 8 to 12 days after vaccination. In our recent experience, between 1% and 5% of people needed to miss a day or two of work after vaccination.

The Blister at the Vaccination Site After your vaccination, a red blister will appear. The blister will vary in appearance depending on your natural skin coloring. Here are some examples.


The blister should turn white 4 to 8 days after vaccination.


Then it will crust over and turn into a scab.


This picture shows what a successful vaccination site looks like.


Adverse Reactions

Adverse reactions can range from discomfort to life threatening. The most common adverse reaction is the spread of the vaccine virus to another part of the body (eyes, mouth, etc). Other more serious types of adverse reactions include serious skin reactions and inflammation of the brain (encephalitis).


Get medical care right away if you think you might be having an adverse reaction to your vaccination.

Screening to Prevent Adverse Reactions Some people should not get smallpox vaccine, except under emergency situations.
People whose immune system is not working fully (due to disease, medication, or radiation), such as HIV/AIDS, cancer, transplant, immune deficiency.

People diagnosed with eczema or atopic dermatitis, now or earlier in life.

People with current skin conditions, such as burns, impetigo, contact dermatitis, chickenpox, shingles, psoriasis, or uncontrolled acne, until the condition clears up.

Pregnant women.

People with a household contact who meets any of the conditions above.

People with serious heart or vessel conditions (such as angina, heart attack, artery disease, congestive heart failure, stroke, other cardiac problem).

People with 3 cardiac risk factors (smoking, high blood pressure or cholesterol, diabetes, family history).

People taking steroid eye drops or ointment.

Breastfeeding mothers.

Anyone who had problems after previous doses or is allergic to the vaccine or any component.

Note: In the event of a smallpox outbreak, even people with the above exemptions should get smallpox vaccination

Statistical Data on Adverse Reactions
In the past, about 1,000 out of every 1,000,000 vaccinated people experienced reactions that were serious, but not life-threatening. Most of these reactions involved spread of vaccine virus elsewhere on the body. In the past, between 14 and 52 people out of 1,000,000 vaccinated for the first time experienced potentially life-threatening reactions. From past experience, one or two people in 1 million who receive smallpox vaccine may die as a result.

Serious side effects are generally more rare after revaccination, compared to first vaccinations.

After the first 450,000 military smallpox vaccinations between December 2002 and June 2003, few serious reactions occurred. Careful screening and education lowered the adverse event rate below the rates seen historically.

A few dozen first-time vaccinees had chest pain due to myo-pericarditis (inflammation in or around the heart). These cases ranged from mild to moderate; a few of the cases were serious.

A few heart attacks, some fatal, have been reported after smallpox vaccination. At this time, they are not believed to be caused by vaccine. DoD medically exempts people with heart conditions. Further investigation is underway.

Treatment for Adverse Reactions
Vaccinia Immune Globulin (VIG) can help people who have certain serious reactions to smallpox vaccine. A second drug, cidofovir, may be used is some situations. Neither drug is currently licensed for this purpose and they may have side effects of their own. Each would be administered under an investigational new drug (IND) program with the informed consent of the recipient.