Which sequence best describes the basic immune response to a COVID-19 vaccine?

• A. Vaccine makes spike protein in cells
• B. Immune cells detect protein and make antibodies
• C. Antibodies bind protein on real virus and protect
• D. All of the above

Answer: (D)

Vaccines train the immune system by introducing an antigen and then letting the body respond in a coordinated way. In many COVID-19 vaccines, cells are instructed to produce the spike protein themselves, so the body actually makes the protein. This protein is detected by immune cells, which activate and produce spike-specific antibodies. Those antibodies circulate and can bind to the spike protein on the real virus, blocking its ability to infect cells and providing protection. So the sequence includes the body making the antigen, the immune system recognizing and mounting an antibody response, and the antibodies neutralizing the virus—exactly what all of the above describes.