vaccine

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vaccine A liquid preparation of treated disease-producing microorganisms or their products used to stimulate an immune response in the body and so confer resistance to the disease (see immunization). Vaccines are administered orally or by injection (inoculation). They take the form of dead viruses or bacteria that can still act as antigens, live but weakened microorganisms (see attenuation), specially treated toxins, or antigenic extracts of the microorganism.

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