COVID-19 survivors may possibly have protective immunity against severe illness from the SARS-CoV-2 virus for months, or even years just after the infection, a study suggests.
The findings, primarily based on analyses of blood samples from 188 COVID-19 patients, recommend that almost all survivors of the illness have the immune cells needed to fight re-infection.
“Our data suggest that the immune response is there — and it stays,” Professor Alessandro Sette from La Jolla Institute for Immunology in the US.
The researchers measured antibodies, memory B cells, helper T cells and killer T cells — all 4 elements of immune memory — at the very same time.
The study, published in the journal Science, aids clarify some regarding information from other institutes, which showed a dramatic drop-off of COVID-fighting antibodies in the months following infection.
Some feared that this decline in antibodies meant that the body wouldn”t be equipped to defend itself against reinfection.
Sette explained that a decline in antibodies is quite typical.
“Of course, the immune response decreases over time to a certain extent, but that”s normal,” he noted.
“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 added.
The researchers discovered that virus-particular antibodies do persist in the bloodstream months just after infection.
They mentioned the body also has immune cells named memory B cells at the prepared, adding that if a particular person encounters SARS-CoV-2 once again, these cells could reactivate and generate antibodies to fight re-infection.
The SARS-CoV-2 virus makes use of its “spike” protein to initiate infection of human cells, so the researchers looked for memory B cells particular for the SARS-CoV-2 spike.
They discovered that spike-particular memory B cells basically improved in the blood six months just after infection.
“COVID-19 survivors also had an army of T cells ready to fight reinfection. Memory CD4+ “helper” T cells lingered, ready to trigger an immune response if they saw SARS-CoV-2 again,” the researchers mentioned.
Many memory CB8+ “killer” T cells also remained, prepared to destroy infected cells and halt a reinfection, they mentioned.
“The different parts of the adaptive immune systems work together, so seeing COVID-fighting antibodies, memory B cells, memory CD4+ T cells and memory CD8+ T cells in the blood more than eight months following infection is a good sign,” mentioned LJI Professor Shane Crotty.
“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,” Crotty mentioned.
However, the researchers cautioned that protective immunity does differ considerably from particular person to particular person.
They saw a one hundred-fold variety in the magnitude of immune memory.
“People 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,” the researchers mentioned.