A new study conducted by researchers, including those from Monash University, Australia, has said that Covid-19 survivors have immune memory that can at least last for eight months and give them protection against reinfection.

The study, published in the journal Science Immunology, revealed that specific cells within the immune system called memory B cells, “remember” the infection by the virus. So, if a person gets re-exposed to the virus, the B cells trigger a protective immune response through the rapid production of protective antibodies.

This also provided strong evidence for the likelihood that Covid-19 vaccines will work for long periods.

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For the study, the researchers recruited a cohort of 25 Covid-19 patients and took 36 blood samples from them from Day 4 post-infection to Day 242 post-infection.

The scientists found that antibodies against the virus started to drop off 20 days post-infection.

However, they said all patients continued to have memory B cells that recognised one of two components of the virus — the spike protein which helps the virus enter host cells, and the nucleocapsid proteins.

Based on their analysis, the researchers said these virus-specific memory B cells were stably present upto eight months after infection.

The scientists speculated that their study gives hope to the efficacy of any vaccine against the virus. It also explains why there have been very few cases of reinfection across the millions of those who have tested positive for the virus globally.

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Study co-author Menno van Zelm, from the Monash University Department of Immunology and Pathology, said in a statement: “These results are important because they show, definitively, that patients infected with the Covid-19 virus do, in fact, retain immunity against the virus and the disease.”

“This has been a black cloud hanging over the potential protection that could be provided by any Covid-19 vaccine and gives real hope that once a vaccine or vaccines are developed, they will provide long-term protection,” van Zelm said.

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