Catching a cold from another coronavirus strain will not protect you from COVID-19

PHILADELPHIA, Pa. — Studies have suggested that if you have a cold, it’s very unlikely you’ll get another illness like the flu at the same time. In that same light, there’s been some speculation that developing antibodies to less harmful coronavirus strains will protect the body from COVID-19. Unfortunately, a new study finds this probably isn’t true. Researchers from the University of Pennsylvania say antibodies to seasonal coronaviruses (CoVs) which cause the common cold won’t help during the pandemic.

Study leader Scott Hensley says previous studies have hinted at seasonal CoV antibodies being able to fight off SARS-CoV-2, the virus causing COVID-19. While the new study finds some of these antibodies can actually target multiple strains of coronavirus, including SARS-CoV-2, they don’t have the ability to stop the virus entirely.

“We found that many people possessed antibodies that could bind to SARS-CoV-2 before the pandemic, but these antibodies could not prevent infections,” Hensley, an associate professor of Microbiology at the Perelman School of Medicine, says in a university release. “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.”

Your body makes ‘cross reactive’ coronavirus antibodies

The study looked at hundreds of different blood samples taken before the start of the pandemic. Researchers discovered that over 20 percent of the samples contained “cross reactive” anti-CoV antibodies. These blood proteins bind to normal CoV strains as well as key areas on the SARS-CoV-2 cells.

In one analysis of 431 blood samples, coming from 263 children at the Children’s Hospital of Philadelphia and 168 adults at the Penn Medicine Biobank, Hensley’s team found these cross reactive antibodies can attach to the outer spike protein or the nucleocapsid protein of SARS-CoV-2. These are the two key points where the immune system can gain access to the virus. The spike protein is also the main tool the virus uses to attack human cells.

Researchers then looked at old blood samples of 251 people who went on to contract COVID-19. They matched these samples to 251 people who have not been infected during the pandemic. The team again discovered about 20 percent of the group’s pre-pandemic antibodies are cross reactive with SARS-CoV-2; attacking the same virus proteins. Despite this, similar numbers of both the infected and uninfected groups carried these antibodies. This leads researchers to believe old coronavirus antibodies are not effective against COVID.

Hensley’s team adds that the group who later contracted COVID-19 did not see any benefit from having cross reactive antibodies when it comes to the severity of their COVID infection. Patients with cross reactive antibodies did not see any lower rates of hospitalization or ICU visits.

The team did find, in a third test of 27 hospitalized COVID-19 patients, that levels of these antibodies strongly increase during the course of a COVID-19 illness.

Do these antibodies explain why kids don’t get COVID?

Researchers say the analysis on the children reveals both kids and adults have similar levels of cross reactive CoV antibodies. Hensley believes this points to the antibodies not being the reason children seem to be less vulnerable to COVID-19.

Over the last year, the pandemic has infected more than 100 million people worldwide and killed over two million. While age may play a role, scientists are still baffled by what makes the virus deadly to some patients and relatively harmless to others — especially kids.

Antibodies have been a key focus for COVID researchers. The fact that seasonal coronaviruses which cause colds regularly circulate through the population has made them a prime suspect in providing partial immunity. The new research, however, finds something else is probably protecting these people — not their previous bout with a cold.

The team recommends studying other types of immune response, like the body’s T cells, to see if they also have their own cross reaction abilities.

The study appears in the journal Cell.

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