Immunity against COVID-19 could last for 7 months: Study

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New Delhi (NVI): The immunity against coronavirus might persist for up to seven months after being infected with the SARS-CoV-2 virus, according to a new study.

The study led by an Indian-origin researcher in the United States studied the production of antibodies from a sample of nearly 6,000 people infected with the novel coronavirus, the World Economic Forum (WEF) reported.

“We clearly see high-quality antibodies still being produced five to seven months after SARS-CoV-2 infection,” Deepta Bhattacharya from the University of Arizona in the US was quoted as saying by the WEF.

“Many concerns have been expressed about immunity against COVID-19 not lasting. We used this study to investigate that question and found immunity is stable for at least five months, he added.

According to the study, when a virus first infects cells, the immune system deploys short-lived plasma cells that produce antibodies to immediately fight the virus. Those antibodies appear in blood tests within 14 days of infection.

The second stage of the immune response is the creation of long-lived plasma cells, which produce high-quality antibodies that provide lasting immunity.

Bhattacharya led the study and published it in a scientific journal Immunity alongside professor Janko Nicolich Zugich, tracked antibody levels over several months in people who tested positive for SARS-CoV-2 antibodies.

They found SARS-CoV-2 antibodies are present in blood tests at viable levels for at least five to seven months, although they believe immunity lasts much longer.

Earlier studies extrapolated antibody production from initial infections and suggested antibody levels drop quickly after infection, providing only short-term immunity.

Bhattacharya also said that those conclusions focused on short-lived plasma cells and failed to take into account long-lived plasma cells and the high-affinity antibodies they produce. “The latest time-points we tracked in infected individuals were past seven months, so that is the longest period of time we can confirm immunity lasts,” he added.

Bhattacharya further pointed out that people who were infected with the first SARS coronavirus, which is the most similar virus to SARS-CoV-2, are still seeing immunity 17 years after infection.

“If SARS-CoV-2 is anything like the first one, we expect antibodies to last at least two years, and it would be unlikely for anything much shorter.”

The study began when both members of the University of Arizona, led a team that developed a blood test to check for SARS-CoV-2 antibodies. The partnership with the state led to 5,882 volunteers undergoing antibody testing in Pima County, starting April 30. The testing efforts later were expanded statewide.

Zugich also said, “When we began, the first test we developed was 99 per cent accurate for measuring antibodies in one part of the virus. We then decided to confirm, and hopefully improve, that accuracy level by looking at another part of the virus that makes antibodies independent of the first location.”

The scientific verification of the high level of accuracy of the new antibody test is the other finding in the new paper. Of 5,882 tests completed, only one returned a false positive, a rate of less than .02 per cent. The test received US Food and Drug Administration (FDA) emergency use authorization in August.

However, the team now has tested almost 30,000 people and antibody tests still are available for anyone in Arizona age 18 and older at multiple locations throughout the state, Nikolich Zugich said.

-RJV