London testing expert Dr Quinton Fivelman says that if you have had the Omicron variant of Covid recently you could already be protected against a serious influenza infection this winter.

Dr Fivelman, who is chief scientific officer with the London Medical Laboratory, said: “Finally, there may be a silver lining to the pandemic cloud. There’s strong evidence that catching the latest Omicron variants of Covid can protect you from serious influenza.

"However, that does not apply to previous Covid variants such as Delta.

Earlier this year, London Medical Laboratory noticed a correlation between the patients who reported catching Covid and extremely low influenza infection rates. However, because flu cases are lower during the warmer months this was difficult to verify.

Now, research from Prof. Martin Michaelis and teams from the University of Kent and from Germany show a direct link between catching the latest Omicron variants of Covid-19 and gaining protection against flu. It seems a response from the body caused by fighting the Omicron variant also stops the influenza virus from replicating.

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Dr Fivelman added that a new study, ‘Omicron inhibits influenza A virus infection’, shows that Omicron BA.1 and BA.5 (the commonest sub-variant) induces a pronounced interferon response that suppresses influenza A virus replication. Influenza Type A is by far the most common cause of flu in humans.

“Interferons are proteins that tell our immune system that viruses such as Omicron are in our body, triggering immune cells to fight those invaders," he explained.

“Intriguingly, the study also reveals that these interferons are not created in response to previous versions of Covid, such as Delta. However, both Omicron sub-variants tested caused the production of biologically active type I and III interferons and protected cells from super-infection with influenza A viruses.

“The study makes the same connection as London Medical Laboratory’s own observations that, while influenza-like illnesses surged during the Delta wave in England, their spread rapidly declined upon the emergence of Omicron.”

Covid booster and flu shot?

Which leaves open the question of whether to combine a Covid booster with a flu virus vaccine, as now advised by the HSE. Infectious disease expert Monica Gandhi of the University of California at San Francisco said it wouldn’t do any harm, and that a British study found neither an increase in adverse effects nor an increase in boosting antibodies.

However, Katrine Wallace, an epidemiologist at the University of Illinois at Chicago, advises being able to take a day off after a combination of the latest booster and the flu shot, or even just the booster, following anecdotal reports of extreme lethargy and flu-like symptoms lasting for 24 to 36 hours.

Wallace said: “The best way to make sure you’re protected from contracting Covid and spreading it to others is to get vaccinated and boosted. But when you do get boosted, it’s not a bad idea to make sure you can take the next day off.”

Fivelman, of course, does not advocate trying to get Covid rather than the flu vaccine.

“We should not consider Omicron to be in any way safer or somehow preferable to influenza. The latest research shows that Omicron is just as likely as previous Covid variants to lead to cases of long Covid, with 34% of all long Covid cases having developed during the Omicron-era.

“The good news is that if you are unfortunate enough to catch Omicron, the interferons your body produces could well protect you against a severe case of flu.”