The most important COVID-19 attribute to be thankful for this Thanksgiving Day.

As many more people are enjoying a normal Thanksgiving this year, it is time to take measure of the many ongoing issues surrounding COVID-19. Despite the current wave of infections there are many positives, including effective vaccines, monoclonal antibodies, and newly identified anti-viral drugs. These approaches help prevent serious illnesses and deaths despite the incredibly high levels of new infections caused by the Delta virus variant. 

However, the most important thing to be thankful for is the virus has not mutated in a way that escapes either immunity from prior infection or vaccine induced immunity. If that had happened, each “wave” of infection would be worse than the last.

Vaccine uptake could be much better, which would reduce hospitalizations and deaths going forward. However, in most individuals, immunity from vaccination and prior infections has blunted the worst outcomes. 

The key to this is the way the virus infects humans. Unlike influenza (flu), which can bind to almost any protein on any cell in the nose, throat or lungs, COVID-19 must bind to a specific protein on respiratory cells in a very definitive way. This involves the spike protein and the virus binding to a protein called ACE2 on human cells.

The COVID-19 virus (SARS-CoV-2) binds to only one specific protein to infect human cells. Also, only a very small part of the spike protein is involved in binding.

In order to make effective immunity to COVID-19 we have vaccinated with spike protein either in or made by the vaccine. This has made antibodies that bind to the spike protein and block infection in cells, as well as cellular immunity that kills infected cells that are producing virus.

Antibodies to the spike protein block the binding of the virus to human cells and prevent infection.

If the virus were to change (mutate) the spike protein, it could remove the parts where the antibody binds which would allow it to escape immunity. Fortunately, so far even the most infectious COVID-19 strains, such as the Delta variant, have not changed the spike protein enough to escape immunity. This is why the “booster” shots are the same vaccines as the originals.

The reason for this is likely that mutations in the spike protein significant enough to escape immunity also reduce the ability of the virus to infect human cells by reducing binding to the ACE2 protein. Studies out of Rockefeller University have suggested over 20 different mutations in the spike protein may be necessary to escape immunity. They have not evaluated the ability of a virus with this many mutations to infect human cells.

Currently, there is only one viral variant that is raising concern about immune escape. So far, this virus is in so few individuals that it is not a problem. The future of the pandemic, however, depends on this issue.

If the virus continues to be contained by immunity, then eventually everyone will either have been vaccinated or infected and COVID-19 will die out. If a new variant occurs that escapes immunity, then we will need new vaccines and yearly vaccinations to protect ourselves from future waves of infection.

Let’s pray for the former outcome as we give thanks this year.

Published by jbakerjrblog

Immunologist, former Army MD, former head of allergy and clinical immunology at University of Michigan, vaccine developer and opinionated guy.

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