Antibodies Wane but Other Immune Defenses Remain Alert

By Reuters Staff

September 01, 2021

(Reuters) - A new study may help explain why mRNA vaccines are more effective at preventing COVID-19 hospitalizations and deaths than they are at preventing infection with SARS-CoV-2.

Experiments on blood samples from 61 fully vaccinated adults showed that by six months, neutralizing antibody levels had declined. But "your immune system has a backup," study leader John Wherry of the University of Pennsylvania Perelman School of Medicine told Reuters.

Memory B cells, which produce new antibodies if they encounter the virus later on, had increased and become better at recognizing viral variants, his team reported on bioRxiv ahead of peer review.

In the lab experiments, B-cell production of antibodies took a few days to get underway, which may explain why vaccinated individuals face higher risks for infection than for hospitalization and death. The antibodies that can immediately neutralize the virus and prevent initial infection decline over time, but within a few days of encountering the virus, these other immune responses "do kick into action and prevent severe disease," Wherry said.

SOURCE: bioRxiv, online August 23, 2021.