The common cold could offer some level of protection against Covid-19 infection and may explain why children are less likely to exhibit serious symptoms, Glasgow scientists believe.

Research found that human rhinovirus, the virus that causes the common cold, triggers an innate immune response that seems to block SARS-CoV-2 replication in cells of the respiratory tract.

In further studies, mathematical simulations showed that this virus-virus interaction might have a population-wide effect, and that an increasing prevalence of rhinovirus could reduce the number of new Covid-19 cases.

Human rhinoviruses cause the common cold and are the most widespread respiratory viruses found in people. 

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It strengthens previous research which found that common cold antibodies, which are found much more commonly in children aged between 6-16, can provide some protection against the virus.

Research involving UCL Great Ormond Street Institute of Child Health (ICH) found that some people, notably children, have antibodies reactive to SARS-CoV-2 in their blood, despite not ever having being infected with the virus.

These antibodies are likely the result of exposure to other coronaviruses, which cause a common cold and which have structural similarities with SARS-CoV-2 and may offer clues as to why children are not severely impacted by Covid-19.

In the Glasgow study, researchers first infected human respiratory cells with the virus in the lab, recreating the cellular environment in which infections normally occur.

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They then studied the replication of SARS-CoV-2 in these cells, both in the presence and absence of rhinovirus.

Professor Pablo Murcia, from the MRC-University of Glasgow Centre for Virus Research, said: “Our research shows that human rhinovirus triggers an innate immune response in human respiratory epithelial cells which blocks the replication of the Covid-19 virus, SARS-CoV-2.

"This means that the immune response caused by mild, common cold virus infections, could provide some level of transient protection against SARS-CoV-2, potentially blocking transmission of SARS-CoV-2 and reducing the severity of Covid-19.

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"When we used mathematical models, we showed that when rhinovirus circulates at high levels, it decreased the number of new Covid infections. Something to important to keep in mind is that we know that rhinoviruses are highly prevalent in children.

"We know that in Scotland, around 40% of infections are observed in children under five so therefore our research could explain, in part, the differences that we see in Covid-19 disease in children and adults.

"This kind of research could be used in many different ways, it's very exciting. What this is showing or suggests is that the viruses interact with one another. A couple of years ago we showed that the same rhinovirus interacts with the influenza virus. 

"This experimental work allows us to now to try to understand the mechanisms which underpin these interactions at the molecular level. If we understand this, it could lead to the development of new therapies and approaches against Covid-19 such as anti-viral drugs.

“In the meantime, vaccination is our best method of protection.

The study, ‘Human rhinovirus infection blocks SARS-CoV-2 replication within the respiratory epithelium: implications for COVID-19 epidemiology’ is published in the Journal of Infectious Diseases.