Affinity maturation:
In immunology, affinity maturation is the process by which TFH cell-activated B cells produce antibodies with increased affinity for antigen during the course of an immune response. With repeated exposures to the same antigen, a host will produce antibodies of successively greater affinities. A secondary response can elicit antibodies with several fold greater affinity than in a primary response. Affinity maturation primarily occurs on surface immunoglobulin of germinal center B cells and as a direct result of somatic hypermutation (SHM) and selection by TFH cells. [Wikipedia]
Noted in “Covid booster shots are pushing protection to unexpected heights,” Clare Wilson, NewScientist (4 December 2021):
Several other vaccines require three doses, such as the one against the liver infection hepatitis B. Giving sequential doses takes advantage of the fact that when we repeatedly encounter a pathogen or vaccine, our antibody-making cells undergo a process called “affinity maturation”.
Our antibodies are made by immune cells called B-cells, and during affinity maturation, these multiply within the body’s lymph nodes while undergoing mutations. Only the B-cells that make the best antibodies survive and replicate, so as a result, their progeny make ever-stronger antibodies. “With other infections, the third booster protects you for longer and also gives you antibodies that have higher affinity,” says [Paul Hunter at the University of East Anglia, UK]
