Any person with a weakened immune system, including patients with cancer or HIV infection should NOT receive the smallpox vaccine. People who have close contact with a person having any of these conditions also should not get the smallpox vaccine. That means parents, siblings and caregivers of St. Jude patients should not be immunized against smallpox. St. Jude patients could catch the virus by touching a person who has been immunized or by touching objects that have been touched by a person who received the vaccine.