Why do vaccines come with risks? i'm in 9th grade taking biology and we learned that vaccines are dead viruses which provoke immune response so the immune system recognizes the virus and knows how to fight it in the future. then why do some vaccines say d

Everyone's different: Excellent question. Your description of how vaccines work is generally true (though not all vaccines are dead- for example, the chicken pox vaccine). The majority of the risks comes from the fact that each person has a slightly different response vaccines- depending on genetics some people have an immune system can "over-react" and cause damage to their own bodies rather than against the microbe.