New Study Suggests Added Protection Against COVID-19 From Previous Common Cold Or Flu Infections

A new study published Monday in the weekly international journal Nature suggests that exposure to current endemic coronaviruses, which can include the common cold and the flu, could supply added protection against COVID-19 and its variants like Delta and Omicron.

Obviously, many people get the common cold or the flu within their lifetimes, but there are those who get extremely sick or die from COVID-19 who likely contracted these endemic coronaviruses previously. However, not every common cold results from a coronavirus.

It is also worth emphasizing that exposure to and contraction of a common cold or one of the four endemic coronaviruses, besides less common ones like MERS and SARS, are not replacements for vaccination and do not offer the same protection.

Dr. Simon Clarke, Associate Professor in Cellular Microbiology at the University of Reading, had this to say about the study: “It could be a grave mistake to think that anyone who has recently had a cold is protected against Covid-19, as coronaviruses only account for 10-15% of colds.”

The study, titled “Pre-existing polymerase-specific T cells expand in abortive seronegative SARS-CoV-2,” suggests that T-cells (types of white blood cells that protect against infection), present in healthcare workers who took part in the study exhibited enhanced protection that could result from previous exposure to or infection by one of the four endemic coronavirus infections.

Previous exposure could cause an asymptomatic case of COVID-19 (reducing the likelihood of detection) to protect against infection, and/or could reduce the severity of symptoms. COVID-19 is a coronavirus, so the T-cells pointed out in this study could also be the result of a previous asymptomatic or undetected COVID-19 infection(s).

All coronaviruses share similar traits, so a body previously exposed to a coronavirus can recognize those similar aspects and better defend itself against COVID-19. However, previous exposure to a coronavirus does not offer blanket protection as some headlines about the study are suggesting.

“These T-cells [a possible result of the previous infection by coronaviruses] did not attack the virus directly or kill cells which it had invaded, but produced molecules that stimulate the activity of other types of white blood cells which would tackle the infection,” Clarke added.

Evidence of a previous infection from a coronavirus -- there are seven possibilities, though not all of them are common,or endemic — could explain why one person in a household tests positive while additional members of that household either do not test positive for or contract COVID-19. It could also explain a variation in symptoms, including severity, among members of a household or group of people similarly exposed.

A retired consultant in Communicable Disease Control, former editor of Vaccines in Practice, and past Chair of the BMA Public Health Medicine Committee, Dr. Peter English, said of the study:

“We should remember that nearly everybody has been infected with a wide range of common cold viruses, and this does not appear to have provided much protection during the pandemic; although – as this study shows – it might partly explain some of the differences in the way people have responded.”

This study does not go into whether there is a difference between the benefits of the infection from the four endemic, common coronaviruses and less common but more severe than deadly coronaviruses like MERS or SARS. More research is necessary to figure out how much protection the common cold or the flu adds when helping someone fight off a COVID-19 infection or reducing their risk of infection.