Vaccines are
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Same as monoclonal antibodies
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Treated bacteria or viruses or one of their proteins
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MHC proteins
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Strands of nucleic acids
Some vaccines contain live, attenuated (weak or inactivated) microorganisms. Although most attenuated vaccines are viral, some are bacterial in nature. Examples include the viral diseases yellow fever, measles, rubella, and mumps, and the bacterial disease typhoid. The live Mycobacterium tuberculosis vaccine contains a virulently modified strain called BCG used to elicit an immune response to the vaccine. The live attenuated vaccine-containing strain Yersinia pestis is used for plague immunization. Rather than introducing an inactivated or attenuated micro-organism to an immune system, a fragment of it (protein subunit) can create an immune response. Examples include the subunit vaccine against hepatitis B virus that is composed of only the surface proteins of the virus, the virus-like particle (VLP) vaccine against human papillomavirus (HPV) that is composed of the viral major capsid protein.