COVID-19 infection creates immunity for at least six months

Henrietta Strickland
November 21, 2020

The researchers analyzed blood samples collected at various ahses of the disease following the onset of symptoms, with some collected more than six months later.

"By studying these multiple compartments of adaptive immunity in an integrated manner, we observed that each component of SARS-CoV-2 immune memory exhibited distinct kinetics", the researchers wrote in the study.

The study, led by scientists at La Jolla Institute for Immunology at San Diego university in the USA, assessed elements of the immune response including antibodies and T-cells, and found the "immune memory" may last for at least eight months. Humans make SARS-CoV-2-specific antibodies, CD4+ T cells, and CD8+ T cells in response to SARS-CoV-2 infection.

T cells are considered fundamental to define the durability of the immune response after a coronavirus diagnosis as, "T cell memory might reach a more stable plateau, or slower decay phase, later than the first six months post-infection", the study reads. The researchers said that there was about a 200-fold range in the level of antibody responses among the adults. Government scientists think the Covid epidemic could now be in retreat.

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.

These findings suggest that in clinical practice, repeat PCR testing may not be needed to deem that a patient is no longer infectious, as this could remain positive for much longer and does not necessarily indicate they could pass on the virus to others. 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.

Thirumala-Devi Kanneganti vice chair of St. Jude Immunology.- ST. JUDE CHILDREN'S RESEARCH HOSPITAL
Study: Coronavirus immunity can last up to 8 months

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".

This "spike" is what numerous vaccines in development target.

"We were excited to connect these dots to understand how TNF-alpha and IFN-gamma trigger PANoptosis", said co-first author Rajendra Karki, a scientist in the Kanneganti laboratory.

It also looked at isolation of the live virus - a stronger indicator of a person's infectiousness, as the live virus is isolated and tested to see if it can successfully replicate in the laboratory.

It comes as the health secretary told Sky News he hoped a mass vaccination programme for COVID-19 would get under way "within a matter of weeks".

Existing research says that people with COVID-19 may be contagious anywhere between two to three days before symptoms surface, and that they may be most likely to spread the virus during the 48 hours before exhibiting symptoms, Harvard Medical School experts say.

Other reports by Click Lancashire

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