Previous coronaviruses infection may lessen severity of Covid-19
Being previously infected with a coronaviruses that cause the 'common cold' may decrease the severity of (SARS-CoV-2) infections, the virus behind Covid-19, say researchers, including one of Indian-origin.
The study, published in the Journal of Clinical Investigation, however, also demonstrated that the immunity built up from previous non-SARS-CoV-2 coronavirus infections does not prevent individuals from getting Covid-19.
The findings provide important insight into the immune response against SARS-CoV-2, which could have significant implications on Covid-19 vaccine development.
"Our results show that people with evidence of a previous infection from a "common cold" coronavirus have less severe Covid-19 symptoms," said study author Manish Sagar from Boston University in the US.
While SARS-CoV-2 is a relatively new pathogen, there are many other types of coronaviruses that are endemic in humans and can cause the "common cold" and pneumonia.
These coronaviruses share some genetic sequences with SARS-CoV-2, and the immune responses from these coronaviruses can cross-react against SARS-CoV-2.
In this 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 coronoavirus 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" coronoavirus.
However, a previous positive test result for a coronavirus did not prevent someone from getting infected with SARS-CoV-2.
Another interesting finding, the authors noted, is that immunity may prevent disease (Covid-19) in ways that are different from preventing infection by SARS-CoV-2.
This is demonstrated by the fact that the patient groups had similar likelihoods of infection but differing likelihoods of ending up in the ICU or dying.