A previous cold coronavirus infection may reduce the severity of Covid-19, the respiratory disease caused by SARS-CoV-2, according to a US study.
- A SARS-CoV-2 infection triggers a cross-immune reaction in people who have previously contracted another coronavirus, which causes colds or pneumonia.
- Previous infection with a cold coronavirus would thus reduce the severity of Covid-19 disease by decreasing the risk of ending up in intensive care or needing respiratory assistance.
- This discovery could not only have repercussions on the development of the vaccine, but also on that of a treatment making it possible to limit the severe forms of Covid-19.
Having been infected with a “benign” coronavirus responsible for the common cold does not provide immunity against SARS-CoV-2. On the other hand, this old contamination would reduce the risk of developing a serious form of Covid-19.
This is the conclusion reached by researchers from Boston Medical Center and Boston University School of Medicine. In a study published in the Journal of Clinical Investigation, they demonstrate that prior infection with a cold coronavirus reduced the severity of Covid-19 disease. This discovery could have significant implications for the development of a future vaccine.
A protective effect from other coronaviruses
To reach this conclusion, the researchers started from the postulate that, if SARS-CoV-2 is a recent pathogen, there are however many other types of endemic coronaviruses in humans. Causing the “cold” or pneumonia, these coronaviruses share certain genetic sequences with SARS-CoV-2. It is therefore possible that immune responses to these other coronaviruses may cross-react against SARS-CoV-2.
The study authors looked at data from the electronic medical records of people who underwent a PCR test between May 2015 and March 11, 2020. The nasopharyngeal PCR test detects various respiratory pathogens, including endemic cold coronaviruses . They also looked at data from people who were tested for SARS-CoV-2 between March 12, 2020 and June 12, 2020.
After adjusting for various factors including age, sex or BMI, the researchers found that patients hospitalized for Covid-19 and who had already obtained a positive PCR test result for another coronavirus presented a significantly lower risk of being admitted to the intensive care unit, or even of needing respiratory assistance. Their probability of survival was also significantly higher. However, a previous positive result for coronavirus did not prevent a person from contracting SARS-CoV-2.
“Our results show that people with evidence of previous cold coronavirus infection have less severe COVID-19 symptoms”confirms Dr. Manish Sagar, a physician specializing in infectious diseases and co-author of the study.
Limit severe forms of infection
The authors draw another interesting conclusion from their work: that immunity can prevent Covid-19 in a different way from preventing SARS-CoV-2 infection. They demonstrated this by the fact that groups of patients had similar probabilities of infection but different probabilities of ending up in intensive care or dying.
“People are regularly infected with coronaviruses other than SARS-CoV-2, and the results of this study could help identify patients at lower or higher risk of developing complications after being infected with SARS-CoV. -2,explains Joseph Mizgerd, professor of medicine, microbiology and biochemistry at Boston University School of Medicine, also co-author of the work. We hope that this study can serve as a springboard to identify the types of immune responses that may not necessarily prevent SARS-CoV-2 infection, but rather limit the damage caused by Covid-19.”
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