Which of the following is an example of an inactivated vaccine?

• A. MMR vaccine
• B. DTap vaccine
• C. Varicella live vaccine
• D. Oral polio vaccine (live)

Answer: (B)

Inactivated vaccines use killed pathogens or their non-replicating components to stimulate immunity. Because the organism can’t reproduce in the body, these vaccines are generally safer for people who are immunocompromised, but they often require booster doses to maintain protection. The example here uses inactivated components of the pathogen—specifically the diphtheria and tetanus toxoids and purified pertussis proteins (acellular pertussis components)—so it cannot cause disease and relies on repeated doses to build and sustain immunity. In contrast, vaccines like those against measles, mumps, rubella; varicella; and the oral polio vaccine contain live, weakened viruses that can replicate to produce strong, lasting immunity, which is why they’re not inactivated vaccines.