Previous infection may lessen severity of COVID-19, study finds

Being previously infected with other types of coronaviruses may decrease the severity of severe acute respiratory syndrome coronavirus (SARS-CoV-2) infections, the virus that causes the novel coronavirus (COVID-19), according to a new study published in the Journal of Clinical Investigation.

Led by researchers at Boston Medical Center and Boston University School of Medicine, the study demonstrates that the immunity built up from previous non-SARS-CoV-2 coronavirus infections does not prevent individuals from getting COVID-19.

For the study, the researchers looked at electronic medical record data from individuals who had a respiratory panel test (CRP-PCR) result between May 18, 2015 and March 11, 2020. The CRP-PCR detects diverse respiratory pathogens including the endemic "common cold" coronaviruses. They also examined data from individuals who were tested for SARS-CoV-2 between March 12, 2020 and June 12, 2020.

After adjusting for age, gender, body mass index, and diabetes mellitus diagnosis, COVID-19 hospitalized patients who had a previous positive CRP-PCR test result for a coronavirus had significantly lower odds of being admitted to the intensive care unit (ICU), and lower trending odds of requiring mechanical ventilation during COVID. The probability of survival was also significantly higher in COVID-19 hospitalized patients with a previous positive test result for a "common cold" coronavirus. However, a previous positive test result for a coronavirus did not prevent someone from getting infected with SARS-CoV-2, according to the study.

The findings provide important insight into the immune response against SARS-CoV-2, which could have significant implications on COVID-19 vaccine development, the researchers said.

"People are routinely infected with coronaviruses that are different from SARS-CoV-2, and these study results could help identify patients at lower and greater risk of developing complications after being infected with SARS-CoV-2," said Joseph Mizgerd, ScD, corresponding author and professor of medicine, microbiology, and biochemistry at the Boston University School of Medicine. "We hope that this study can be the springboard for identifying the types of immune responses for not necessarily preventing SARS-CoV-2 infection but rather limiting the damage from COVID-19."

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