Researchers are looking at whether the common cold could offer some protection against contracting Covid-19.
A recent study by scientists at Yale University found that rhinovirus – the most frequent cause of common cold – could jump-start the body’s antiviral defences, providing protection against the flu.
They discovered that the presence of rhinovirus triggered production of the antiviral agent interferon, which is part of the early immune system response to invasion of pathogens.
The researchers are now looking at whether introduction of the cold virus before infection by the Covid-19 virus offers a similar type of protection.
Dr Ellen Foxman, of the Yale School of Medicine, told the PA news agency: ‘The common cold virus triggers the normal antiviral defences of these cells that form the lining of the airway.
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‘So the cells that form the lining of the airway is where all these viruses need to go to grow.
‘That includes flu, common cold, Covid-19 – basically all the viruses that you get by breathing them in, they all grow in this tissue that forms the lining of your airway.’
She added: ‘This response, the interferon response, which is this general defence mechanism against all viruses, we know that response does work against Covid-19.
‘If you do the experiment in a lab, you can apply this chemical – interferon – to cells, then you can block the virus that causes Covid-19 as well.
‘So it’s possible that we’ll see the same thing, but we’re just beginning to do the experiments.
‘Sometimes you see unexpected things happening so you have to just do the experiment and see what the result is and that that’s just a work in progress at the moment.’
Dr Foxman said she thought interferon-based immunity lasted about a week, maybe up to two, adding that it did not prevent infection forever.
But she explained it may provide a ‘temporary buffer against getting another virus’ while the body is all ‘revved up’ to fight it.
However, the expert said while she was sure this could be applied to flu, Covid-19 is unpredictable.
‘One unpredictable thing is the entry receptor that Covid-19 uses to get inside your body – there have been some reports that can be increased by interferon.
‘So, we just have to test how important is that, compared to having these antiviral defences at the ready,’ Dr Foxman explained.
She told PA interferon defences can be very potent against a lot of viruses, but that they only work early in infection as they stop the virus from growing.
Dr Foxman said interferons are already used as antiviral treatments for other conditions, and trials looking at their use in combating Covid-19 indicate that if given early enough in infection, there may be some benefit.
She added: ‘Maybe we can think harder about just triggering this general response as a way of temporarily protecting people who are at high risk – who are in high risk of being exposed.’
However, Dr Foxman warned that interferon response triggers a lot of the same symptoms as a cold, ‘but when you’re talking about preventing a more serious virus maybe it does make sense’.
She told PA that catching the virus early was key as it is a very short-term defence, and contact tracing was a good way to do this.
It could also make people more inclined to participate in contact tracing, if they knew there was an early intervention available, Dr Foxman continued.
However, she stressed that this was all speculation and that the studies still needed to be conducted.