What are the main types of vaccines used in immunization programs?

• A. Inactivated/killed vaccines and live attenuated vaccines (plus subunit/recombinant for some diseases).
• B. Subunit/recombinant vaccines only
• C. Live attenuated vaccines only
• D. Inactivated/killed vaccines only

Answer: (C)

Vaccines are categorized by how the antigen is presented to the immune system. The traditional, broad distinction centers on two main approaches: live attenuated vaccines, which use a weakened form of the pathogen that can still replicate and provoke a strong, long-lasting immune response, and inactivated/killed vaccines, which use a pathogen that has been inactivated so it cannot replicate but can still stimulate immunity. In addition to these, many vaccines now use subunit or recombinant technologies that deliver specific proteins or antigens from the pathogen, offering targeted protection with typically greater safety for certain groups. Some vaccines also rely on toxoids or conjugates, depending on the disease, but the key idea is that immunization programs draw on both live attenuated and inactivated vaccines, with subunit/recombinant approaches used for particular diseases.