Prior Exposure to Common Cold Won't Shield You From COVID: Study

THURSDAY, Feb. 11, 2021 (HealthDay News) -- It would be nice if it were true, but a bout of the common cold won't protect you against the new coronavirus infection, researchers report.

Colds are caused by seasonal coronaviruses (CoVs) and previous studies have suggested that exposure to cold coronaviruses may safeguard against the SARS-CoV-2 coronavirus that causes COVID-19.

To find out if that was true, researchers analyzed blood samples collected from hundreds of people before the COVID-19 pandemic.

More than 20% of the samples had CoV antibodies that could theoretically bind to both cold-causing CoVs and to key sites on SARS-CoV-2.

However, these antibodies didn't reduce SARS-CoV-2 infectivity, and weren't associated with better outcomes in people who later got COVID-19, according to the study published online Feb. 9 in the journal Cell.

The researchers also tested blood from different groups of people and found that, on average, both children and adults tend to have similar levels of CoV antibodies.

This suggests that these antibodies aren't the reason why most children don't develop severe COVID-19, the study authors concluded.

"We found that many people possessed antibodies that could bind to SARS-CoV-2 before the pandemic, but these antibodies could not prevent infections," said study leader Scott Hensley. He's an associate professor of microbiology at the University of Pennsylvania's School of Medicine, in Philadelphia.

"Although antibodies from prior coronavirus infections cannot prevent SARS-CoV-2 infections, it is possible that pre-existing memory B cells and T cells could potentially provide some level of protection or at least reduce the disease severity of COVID-19. Studies need to be completed to test that hypothesis," Hensley said in a university news release.

Larger studies are required to definitively answer the question of whether pre-existing anti-CoV antibodies can protect against SARS-CoV-2 viruses, the researchers said.

But one expert welcomed the findings.

"The idea that having the snuffles a while back somehow protects you from SARS-CoV-2 infection has always left me cold, but it's been a persistent urban legend throughout the pandemic," Dr. John Moore, a virologist at Weill Cornell Medicine in New York City, told The New York Times. "Hopefully, this new paper will finally cool everyone down and put such thoughts into the freezer."

The researchers did say that more studies are needed to assess other types of immune response (such as T cells) to seasonal colds to determine if they provide some amount of cross-reactive protection against COVID-19.

Since the pandemic began more than a year ago, there have been more than 107 million reported infections and more than 2.3 million deaths reported worldwide.

Some risk factors for severe COVID-19 are clear -- such as age -- but it's still not fully understood why some people have mild illness or no symptoms while others become seriously ill. Experts believe that antibodies may be one possible explanation.

More information

The U.S. Centers for Disease Control and Prevention has more on COVID-19.

SOURCES: University of Pennsylvania School of Medicine, news release, Feb. 10, 2021; The New York Times