There is limited evidence of reinfection in humans with previously documented Covid-19, according to the research
A new study suggests that T-cells might provide individuals who have had a mild or asymptomatic case of Covid-19 with lasting immunity against future infection, even if their blood contains no neutralizing antibodies.
Most people who are exposed to Sars-CoV-2, the coronavirus that causes Covid-19, only experience mild symptoms or none at all.
According to the research, published in the journal Cell, there is limited evidence of reinfection in humans with previously documented Covid-19, the Business Insider reported.
However, the infection can still pass from them to other people, and the overall case fatality rate appears to be converging on 0.5%–1.0%.
It is, therefore, important to establish whether individuals who have contracted the virus once can contract it again and become contagious, or whether they are immune to future infection.
Research suggests that not all individuals who have contracted Sars-CoV-2 in the past, produce antibodies capable of neutralizing the virus, particularly if they only experienced a mild infection.
Studies have also found that immune cells known as memory B-cells, which produce antibodies against previously encountered infections, tend to be short-lived after infection with the closely related coronavirus Sars-CoV, which causes severe acute respiratory syndrome (Sars).
In contrast, another type of immune cell, called a memory T-cell, which can recognize a previously encountered pathogen and initiate an immune response to it, may persist for years after the initial infection.
Memory T-cells protect against Sars-CoV-2 infection even in the absence of antibodies against the virus.
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“In the absence of a protective vaccine, it is critical to determine if exposed or infected people, especially those with asymptomatic or very mild forms of the disease who likely act inadvertently as the major transmitters, develop robust adaptive immune responses against Sars-CoV-2,” said Marcus Buggert of the Karolinska Institutet in Sweden, who is the senior author of the study.
The authors of the study examined blood from 206 people in Sweden who had Covid-19 with varying degrees of severity.
They found that regardless of whether a person had recovered from a mild or severe case, they still developed a robust T-cell response. Even coronavirus patients who did not test positive for antibodies developed memory T-cells, the results showed.
Anthony Fauci, the director of the US National Institute of Allergy and Infectious Diseases, called T-cell studies like this one “good news.”
Another study published in July found that in a group of 36 recovered coronavirus patients, all produced memory T-cells that recognize and are specifically engineered to fight the new coronavirus.
One more recent study published in the journal Nature found that among 18 German coronavirus patients, more than 80% developed virus-specific T-cells.