A new study by US researchers found that people who have been exposed to the virus or vaccinated against it can have lasting immunity for eight months. The immunity could persist for decades as well.

The study was published in the journal Biorxiv . In the study, researchers from La Jolla Institute for Immunology in the US analysed multiple types of immune cells in 185 Covid-19 patients, including 41 cases who had recovered from the infection in over six months before the study.

The team measured the levels of antibodies, memory B-cells and T-cells, specific for SARS-CoV-2, in a range of participants, including Covid-19 survivors.

“To our knowledge, this is the first study of its kind, incorporating antigen-specific antibody, memory B cell, CD8+ T cell, and CD4+ T cell measurements, out past six months post-infection,” the researchers wrote in the study.

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In this study, the researchers found that memory B cells, which recognise the spike protein of the SARS-CoV-2 and generate an immune response, were more in abundance after six months of recovery than after one month.

“To our knowledge, this is the first study of its kind, incorporating antigen-specific antibody, memory B cell, CD8+ T cell, and CD4+ T cell measurements, out past 6 months post-infection,” the authors added.

Following an infection, antigen-specific, long-lived memory T cells are formed. Memory T-cells can quickly expand to large numbers of T-cells upon re-exposure to the antigen.

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