Immune system remembers Covid-19 infection for at least six months, say researchers

Recent studies suggest that immunity in COVID-19 infected patients can last for a long while.

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COVID-19 immunity can be different for everybody, according to the findings of several studies. While people with stronger immunity are less susceptible to new coronavirus, others with weaker immunity are at higher risk of severe COVID-19 infections. Then there are people who possess COVID antibodies without having any history of the illness in the first place, researchers say.

A new study published in the journal Naturesuggests that immunity in COVID-19 infected patients can last for a long while, but it is yet to fully determine how long the immune system actually remembers the infection. People may be able to fight off reinfection for at least six months after they recover from Covid-19 thanks to cells that can "remember" the virus, the study states.

Recently, researchers in the United States and Switzerland studied dozens of people who had recovered from Covid-19 and found that while their antibodies may fade over time, they maintained levels of specific memory B cells. These cells can remember the pathogen and can, if faced with reinfection, prompt the immune system to reinitiate the production of virus-fighting antibodies.

"Memory responses are responsible for protection from reinfection and are essential for effective vaccination," concluded the study published in Nature.

"The observation that memory B cell responses do not decay after 6.2 months, but instead continue to evolve, is strongly suggestive that individuals who are infected with SARS-CoV-2 could mount a rapid and effective response to the virus upon re-exposure," the studies states.

The researchers studied 87 people with confirmed COVID-19 diagnosis at a little over one month and six months after infection. They found that virus neutralising antibody activity reduced with time, but the number of memory B cells remained unchanged.

Researchers said their study indicated that the memory B cell response against the coronavirus evolves during the six months after infection in the presence of viral remnant proteins in the body enabling the cells to produce more potent antibodies.

The time it takes to fight off reinfection to the new coronavirus and the various immune process involved could determine the dynamics of COVID-19.

Earlier research showed that neutralising antibodies can reduce quickly after SARS-CoV-2 infection. But other parts of the immune system can play a role in longer immunity, scientists say.

Another study based on the analyses of blood samples from 188 COVID-19 patients and published in the journal Science in January suggests that nearly all major parts of the immune system could continue to respond to the coronavirus for at least eight months. This included protein spike specific memory B cells.


First Published:Jan. 20, 2021, 5:28 p.m.

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