COVID-19 immunity persists for eight months or more

In a new study from the La Jolla Institute for Immunology, researchers have determined that COVID-19 immunity could last for eight months, or possibly even years. The experts report that nearly all coronavirus survivors have the immune cells necessary to fight reinfection.

The researchers analyzed blood samples from 188 COVID-19 patients. Their results indicate that the body’s adaptive immune responses to SARS-CoV-2 provide the body with the ability to fight off this pathogen for at least eight months after the onset of symptoms from the initial infection.

“Our data suggest that the immune response is there – and it stays,” said Dr. Alessandro Sette.

“We measured antibodies, memory B cells, helper T cells and killer T cells all at the same time,” explained Professor Shane Crotty. “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.”

Previous studies documented a dramatic decline in COVID-fighting antibodies in the months following infection, which has caused concern about the body’s ability to defend itself. The new research helps to clarify this data. 

“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,” said Dr. Sette.

The researchers found that COVID-19 antibodies persist in the bloodstream months after infection. Furthermore, after coronavirus infection, the body is equipped with immune cells called memory B cells that can reactivate and produce the antibodies needed to fight reinfection.

The experts looked for memory B cells that specifically recognize the spike protein which is used by SARS-CoV-2 to gain entry into human cells. They discovered that spike-specific memory B cells actually increased in the blood six months after infection. 

In addition, COVID-19 survivors had an army of T cells that were prepared to destroy infected cells more than eight months after the initial infection. 

“This implies that there’s a good chance people would have protective immunity, at least against serious disease, for that period of time, and probably well beyond that,” said Professor Crotty.

The researchers caution that protective immunity varies dramatically from person to person. People with a weak immune memory may be more vulnerable reinfection, and also 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,” said Professor Crotty.

According to Dr. Daniela Weiskopf, it is possible that immune memory will be similarly long lasting similar following vaccination, but further research is needed when the data becomes available.

“Several months ago, our studies showed that natural infection induced a strong response, and this study now shows that the responses lasts,” said Dr. Weiskopf. “The vaccine studies are at the initial stages, and so far have been associated with strong protection. We are hopeful that a similar pattern of responses lasting over time will also emerge for the vaccine-induced responses.”

The researchers will continue to analyze samples from COVID-19 patients and hope to track their responses 12 to 18 months after the onset of symptoms.

“We are also doing very detailed analyses at a much, much higher granularity on what pieces of the virus are recognized,” said Dr. Sette. “And we plan to evaluate the immune response not only following natural infection but following vaccination.”

The study is published in the journal Science.

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By Chrissy Sexton, Earth.com Staff Writer