Question

after a person has been vaccinated against a particular pathogen, he or she often needs to receive injections of the same vaccine, called booster shots, in the future in order to maintain a suf cient level of immunity against that pathogen. booster shots increase the length of time that the person is immune to that particular pathogen. each booster shot increases the number and concentration of a persons
antibodies and memory cells
antibodies and macrophages
amino acids and macrophages
amino acids and memory cells

Explanation:

Booster shots enhance immunity by increasing antibodies and memory cells which help recognize and fight the pathogen. Macrophages are part of the innate immune - system and amino acids are building blocks of proteins, not directly related to the immediate effect of booster shots on immunity.

Answer:

A. antibodies and memory cells