Only live attenuated vaccines can still cause infection. All vaccines can cause illness, but this is commonly a hypersensitivity reaction (similar to an allergic response), not due to the disease itself. Very rarely a serious disease known as eczema vaccinatum can be caused by the smallpox vaccine. Vaccines that use pieces of pathogens often use a carrier virus in the injection. Those with very weak immune systems that are exposed to such a vaccine can become infected with the carrier virus and develop [[eczema]]. A recent case of this was reported in the United States after a military man was vaccinated with smallpox and his two-year-old son became ill.<ref>http://www.associatedcontent.com/article/183349/soldier_infects_toddler_son_with_lifethreatening.html AP article on eczema vaccinatum</ref> | Only live attenuated vaccines can still cause infection. All vaccines can cause illness, but this is commonly a hypersensitivity reaction (similar to an allergic response), not due to the disease itself. Very rarely a serious disease known as eczema vaccinatum can be caused by the smallpox vaccine. Vaccines that use pieces of pathogens often use a carrier virus in the injection. Those with very weak immune systems that are exposed to such a vaccine can become infected with the carrier virus and develop [[eczema]]. A recent case of this was reported in the United States after a military man was vaccinated with smallpox and his two-year-old son became ill.<ref>http://www.associatedcontent.com/article/183349/soldier_infects_toddler_son_with_lifethreatening.html AP article on eczema vaccinatum</ref> |