Study reveals that COVID-19 survivors have immune cells to fight re-infection

A new report from the LaJolla Institute for Immunology has revealed that almost all survivors of COVID-19 have the immune cells necessary to fight re-infection.

Based on analyses of blood samples from 188 COVID-19 patients, the findings suggest that the immune system learns to fight specific pathogens for at least eight months – and longer — after the onset of symptoms from the initial infection.

“Our data suggest that the immune response is there–and it stays,” said Alessandro Sette, professor at LaJolla Institute for Immunology (LII) and co-author of the study.

He conducted the study with LJI Professor Shane Crotty and LJI Research Assistant Professor Daniela Weiskopf.

“We measured antibodies, memory B cells, helper T cells and killer T cells all at the same time,” Crotty said. “As far as we know, this is the largest study ever, for any acute infection, that has measured all four of those components of immune memory.”

The researchers found that virus-specific antibodies persist in the bloodstream months after infection. However, the body also has immune cells called memory B cells. If a person reencounters SARS-CoV-2, these memory B cells could reactivate and produce SARS-CoV-2 antibodies to fight re-infection. Further, the researchers found that spike-specific memory B cells actually increased in the blood six months after infection. COVID-19 survivors also had an army of T cells ready to fight reinfection.

“Of course, the immune response decreases over time to a certain extent, but that’s normal. That’s what immune responses do. They have a first phase of ramping up, and after that fantastic expansion, eventually, the immune response contracts somewhat and gets to a steady state,” Sette said.

The team cautions that protective immunity does vary dramatically from person to person. Those with a weak immune memory may be vulnerable to a case of recurrent COVID-19 in the future, or they may be more likely to infect others.

“There are some people that are way down at the bottom of how much immune memory they have, and maybe those people are a lot more susceptible to reinfection,” Crotty said.

The findings were published in the Jan. 6 online edition of Science. The research was supported by the National Institutes of Health’s National Institute for Allergy and Infectious Disease, the John and Mary Tu Foundation, and the Bill and Melinda Gates Foundation.