Smallpox vaccination is generally a safe and effective means of preventing smallpox. However, in a number of individuals, smallpox vaccination can result in untoward effects and adverse reactions. Most are totally benign, but may be alarming in appearance. Some are serious, but treatable. A few, which rarely occur, are serious, life threatening and can be fatal. Severe adverse reactions are more common in persons receiving primary vaccination compared to those being revaccinated.
In the past, between 14 and 52 people out of 1,000,000 vaccinated for the first time experienced potentially life-threatening reactions. These reactions included serious skin reactions and inflammation of the brain (encephalitis).
From past experience, one or two people per 1 million who received smallpox vaccine died as a result of vaccination side effects. Serious side effects generally are rarer after revaccination, compared to first time vaccinations. Careful screening of potential vaccine recipients is essential to ensure that those at increased risk for serious side effects do not receive the vaccine.
These side effect rates are based on data collected in the United States during the 1960s, when about 300,000 adults got their first smallpox vaccination and over 4,000,000 adults got repeat smallpox vaccinations (revaccinations).
A few heart attacks, some fatal, have been reported after smallpox vaccination. After reviewing these cases, the rate of heart attacks in smallpox vaccinated and unvaccinated people is the same and there is no evidence of a cause-and-effect link between smallpox vaccine and heart attacks. Even so, DoD medically exempts people with heart conditions.
We try to reduce the risk of side effects by exempting people who should not receive this vaccine.
For more information about side effects of the smallpox vaccine please visit http://emergency.cdc.gov/agent/smallpox/vaccination/reactions-vacc-clinic.asp