Immune memory boosts COVID-19 survivors' vaccine response

New data provide a clue as to why some COVID-19 survivors may need only one dose of the two-dose Pfizer/BioNTech and Moderna Inc vaccines. 

Researchers tracked vaccine responses in 11 survivors of mild COVID-19 and 33 never-infected individuals.

In everyone, the vaccines induced the immune system to produce antibodies along with so-called B cells that remember the virus and remain ready to produce new antibodies to fight it, although the magnitude of the B cell response was lower in older people.

Those not previously infected "benefited from both doses," with additional antibody and memory B cell increases after the second shot, researchers reported on Saturday on medRxiv ahead of peer review.

COVID-19 survivors, however, had significant responses to the first dose with no increase in antibodies or memory B cells after the second dose.

Survivors' levels of memory B cells before vaccination correlated strongly with their antibody levels post vaccination, "indicating that these B cells were the likely source" of survivors' boosted antibody levels after just a single shot, said coauthor John Wherry of the University of Pennsylvania.

This suggests memory B cells will play important roles if antibody levels fall over time, he added. Because memory B cells can be the source of new antibodies with some degree of "adaptability," they might play a role in immunity to variant viruses, he speculated. -- Reuters