Holy crap, avoid the smallpox vaccine too!!!!!! Mild to Moderate Problems Mild rash, lasting 2-4 days. Swelling and tenderness of lymph nodes, lasting 2-4 weeks after the blister has healed. Fever of over 100 degrees fahrenheit (about 70% of children, 17% of adults) or over 102 degrees Fahrenheit (about 15%-20% of children, under 2% of adults). Secondary blister elsewhere on the body (about 1 per 1,900). Moderate to Severe Problems Serious eye infection, or loss of vision, due to spread of vaccine virus to the eye. Rash on entire body (as many as 1 per 4,000). Severe rash on people with eczema (as many as 1 per 26,000). Encephalitis (severe brain reaction), which can lead to permanent brain damage (as many as 1 per 83,000). Severe infection beginning at the vaccination site (as many as 1 per 667,000, mostly in people with weakened immune systems). Death (1-2 per million, mostly in people with weakened immune systems).