COVID-19 Reinfection 'Highly Unlikely' For At Least Six Months

Coronavirus immunity in some people may last more than six months, early research suggests

Analyzing the results from the SARS-CoV-2 studies showed that the average length of time of viral RNA shedding into the upper respiratory tract, lower respiratory tract, stool and serum were 17 days, 14.6 days, 17.2 days, and 16.6 days, respectively.

"Our results indicate that antiviral antibodies against SARS-CoV-2 did not decline within 4 months of diagnosis", wrote the authors.

One of these studies, for instance, found that antibody levels "waned quite rapidly" after infection in the British population, suggesting a risk of multiple infections, Health24 reported.

The T-cells - the immune component that both kills off infected cells and helps B-cells make antibodies - were found to still be present at six months. The researchers said that there was about a 200-fold range in the level of antibody responses among the adults.

It is known as the innate immune response and includes the release of chemicals that cause inflammation and white blood cells that can destroy infected cells.

Knowing more about factors affecting how far these droplets travel can inform efforts to control their spread, said study co-author Michael Kinzel from UCF.

They also identified two types of T cells. The researchers however said that more research is needed to determine whether similar findings would emerge among a larger group of people across more time points.


The study, which has not yet been peer-reviewed, took into consideration various immune facets, including B cells, antibodies and T cells.

"T cell memory might reach a more stable plateau, or slower decay phase, later than the first 6 months post-infection", the study states.

Stephen Evans, professor of pharmacoepidemiology at the London School of Hygiene and Tropical Medicine, said it was probably "good news for vaccines being able to provide immunity that is more than very short-term". "Firstly, although most of the cases described here had mild disease, it looks as though their immunity to a second infection is reasonably high".

"We are therefore confident that the majority of people who have survived SARS-CoV-2 infection have some protection against reinfection with SARS-CoV-2", he added.

In this study, the team of researchers at the La Jolla Institute of Immunology in California, and the Icahn School of Medicine at Mount Sinai in NY, investigated multiple compartments of circulating immune memory to SARS-CoV-2 in 185 Covid-19 cases, including 41 cases more than six months post-infection.

The researchers then followed whether staff who had been infected before had the same number of new Covid-19 infections as those who had not been infected before.

But the results of the study, conducted on a group of United Kingdom healthcare professionals - who are among the most at risk of compromising COVID-19 - indicate that relapse cases are rare.

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