Last updated: 09-29-2022

Previous Common Colds Could Boost Risks of More Severe COVID-19


Photograph of a woman with a common cold wrapped in a blanket blowing her nose.


About 30% of common colds are caused by seasonal coronaviruses that are distantly related to SARS-CoV-2. Having had a cold caused by one of those coronaviruses may make some people’s immune systems respond less effectively to infection by SARS-CoV-2, increasing their risk of developing more severe COVID-19 leading to hospitalization or death.

That’s according to a study by University of Rochester researchers funded by NCATS’ Clinical and Translational Science Awards Program and the National Institute of Allergy and Infectious Diseases.

The researchers compared blood samples taken from people before the COVID-19 pandemic to samples taken from people who had severe COVID-19 between April and June 2020. The pre-pandemic samples showed evidence of widespread exposure to two coronaviruses that cause common colds. More than 90% of people included in this study had antibodies to those viruses from before the pandemic.

In COVID-19 cases, people’s immune systems created new antibodies to specifically attack SARS-CoV-2, which is a normal response to a viral infection. Because of the previous exposure to the two common cold coronaviruses, however, people’s immune systems responded to SARS-CoV-2 infection by also making antibodies to those two earlier viruses.

Overall, people who developed severe COVID-19 saw a stronger, speedier rise in all three antibody types — the new SARS-CoV-2 antibodies and the earlier common cold antibodies — compared to people who had only mild or moderate COVID-19.

The new SARS-CoV-2 antibodies attacked the SARS-CoV-2 spike protein at a point that disabled the virus. The common cold antibodies, however, targeted the spike protein at points that did not disable SARS-CoV-2. When the immune system made more common cold antibodies than new SARS-CoV-2 antibodies, people with COVID-19 were more likely to be hospitalized, end up in the intensive care unit or die.

This phenomenon is called “immune distraction,” in which pre-existing antibodies attack newer threats in ways that are less effective for dealing with the newer threat. The researchers say that immune distraction could require the use of updated COVID-19 vaccines to ensure the immune system is primed with antibodies that attack new SARS-CoV-2 variants more successfully. Learn more about the study findings in The Journal of Infectious Diseases.