Could the flu vaccine cut COVID risk?

With flu season underway in Australia and an increasing number of cases already confirmed, people are are already being urged to receive their influenza shot as early as possible. The Victorian government even announced that all Victorians over six months of age will be able to get free flu vaccines at GP clinics and pharmacies.

A recent article from nature.com discussed the possibility of the flu vaccine potentially cutting the risk of COVID. 

“A study of more than 30,000 health-care workers in Qatar found that those who got a flu jab were nearly 90% less likely to develop severe COVID-19 over the next few months, compared with those who hadn’t been recently vaccinated against flu.”

“The study, which was conducted in late 2020, before the roll-out of COVID-19 vaccines, is in line with previous work suggesting that ramping up the immune system using influenza vaccines and other jabs could help the body to fend off the coronavirus SARS-CoV-2.”

A team led by Laith Jamal Abu-Raddad, an infectious-disease epidemiologist at Weill Cornell Medicine–Qatar in Doha, analysed the health records of 30,774 medical workers in the country. The researchers tracked 518 workers who tested positive for SARS-CoV-2. Those who had received an influenza vaccine that season were 30% less likely to test positive for SARS-CoV-2, and 89% less likely to develop severe COVID-19, compared with workers who had not (although the number of severe cases was small in both groups). The study was posted on the medRxiv preprint server on 10 May.

“This is an important piece of evidence,” says Mihai Netea, an infectious-disease specialist at Radboud University Medical Center in Nijmegen, the Netherlands. 

The question of efficacy

How long this protection lasts is unclear. Abu-Raddad said that “I don’t expect to see this effect lasting long at all,” he says. 

It’s not fully clear why flu vaccines, which are composed of killed influenza viruses, would also protect against COVID-19. “Vaccines train the immune system to recognize specific pathogens, but they also rev up broad-acting antiviral defences.” said Netea.

Knowing that vaccines for flu and other diseases can offer protection against COVID-19, even if only partial and for a limited period, could limit the damage caused by a future pandemic before a vaccine for a variant of that disease is developed, Netea argues. “If you have something in the beginning, you could save millions of lives.”

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