Being previously infected with coronaviruses that cause the 'common cold' may decrease the severity of COVID-19, according to researchers, including one of Indian origin, who said the finding could have significant implications on vaccine development.
The study, published in the Journal of Clinical Investigation, also demonstrates that the immunity built up from previous non-SARS-CoV-2 coronavirus infections does not prevent individuals from getting COVID-19.
The researchers at Boston Medical Center and Boston University School of Medicine in the United States noted that 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, they said.
These coronaviruses share some genetic sequences with SARS-CoV-2, and the immune responses from these coronaviruses can cross-react against SARS-CoV-2.
The study looked at electronic medical record data from individuals who had a respiratory panel test 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 hospitalised 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.
They also had lower trending odds of requiring mechanical ventilation during COVID, the researchers said.
The probability of survival was also significantly higher in COVID-19 hospitalised 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.
"Our results show that people with evidence of a previous infection from a "common cold" coronavirus have less severe COVID-19 symptoms," said Manish Sagar, an associate professor at Boston University School of Medicine and the study's co-corresponding author.
The researchers also found that immunity may prevent 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, they said.