Flu jab ‘helped workers avoid COVID-19’: Study

New research released this month suggests those receiving influenza vaccinations may stand a greater chance of avoiding sickness – in particular severe illness – caused by SARS-CoV-2 infection.
 
The Qatar-based pre-print study, which has been picked up by Nature, looked at the health records of 30,774 healthcare workers in the country during the 2020 vaccination season before the availability of COVID-19 vaccines.
 
All of those who took a PCR test during the study period were eligible for inclusion, with effectiveness against SARS-CoV-2 infection and severe or fatal illness the key criteria measured.
 
The findings, which have now been published on medRxiv, indicate that those who were vaccinated had around a 30% reduction in symptomatic COVID-19 infection compared to those who were not, as well as an almost 95% reduction in severe illness.
 
The authors say their research findings were limited by the youth of the cohort, which had an average age of around 36, with the infrequency of severe illness also causing a wide confidence interval for the efficacy estimates.
 
Acknowledging studies that support a link between flu vaccination and COVID-19 prevention and others that do not, they state their work adds to evidence that the flu vaccine may boost protection more widely than for just that specific illness.
 
‘The findings support benefits for influenza vaccination that extend beyond protection against influenza infection and severe disease,’ they wrote.
 
The authors also said that by focusing on the response in healthcare workers, they would be mitigating the influence of a so-called ‘healthy user effect’ as they would be less likely to have wide variations in health-related behaviour compared to the broader population.
 
‘These results for a healthcare worker population where the influence of the healthy user effect is perhaps minimised, support the conclusion that recent influenza vaccination has a genuine biological effect in protecting against SARS-CoV-2 infection and COVID-19 severity,’ the study reads.

For Professor Dale Godfrey, Immunology Theme Leader at the Doherty Institute, the premise of a vaccine designed for one disease offering protection against another is familiar.
 
‘The idea is not a new one,’ he told newsGP. ‘There was a lot of interest in other vaccines possibly providing some protection against COVID.’
 
He points to a study led by the Murdoch Children’s Research Institute which tested the impact of the BCG vaccine against COVID-19 in the first few months of the pandemic.
 
‘There’s evidence even back from the 70s that immunisation with live attenuated vaccines provided a level of protection against influenza,’ he said.
 
‘There was evidence long before COVID that this phenomenon happens and it fits with what we understand.’
 
Professor Godfrey says that even though specific vaccines target the adaptive immune system and will not provide protection against a different virus that does not share the same molecule, the vaccine’s broader impact on the innate immune system may play a role.
 
‘If your immune system has recently been stimulated, then you’ll have a lot of innate cells and innate molecules that will be activated and that takes them a while to settle down again,’ he said.
 
‘And that’s probably what’s happening.
 
‘It’s like putting the immune system on guard, that’s a really key part of any immune response. You’re just revving up your defences a bit against any pathogen.’
 
As for whether people should expect a flu vaccine to protect them against COVID-19, Professor Godfrey is unambiguous that a targeted vaccine is preferable.
 
‘If they want to get a flu vaccine they should certainly do that because it will provide the best protection against flu,’ he said.
 
‘If they’re doing it to get protection against COVID, then a COVID vaccine makes the most sense.
 
‘A flu vaccine might add a little bit to that, who knows, especially if it’s been a few months since their last COVID [vaccine] boost.’
 
The lifespan of any protective boost that might be offered is also not yet clear, Professor Godfrey says.
 
‘It’s not really well understood about the durability of such protection and whether one vaccine is better than another,’ he said.
 
‘Most of the evidence that I’ve heard has been more related to live attenuated vaccines, and the flu vaccine is not a live attenuated vaccine, it’s a subunit vaccine.
 
‘There are lots of questions that still remain.’
 
In the Nature article, infectious diseases expert Professor Mihai Netea from the Radboud University Medical Center in the Netherlands suggests that using an existing vaccine as protection against emerging disease could be helpful in the early stages of any future pandemic.
 
Professor Godfrey believes the huge shift in the dynamics of vaccine development due to COVID-19 is likely to limit the useful window of using an unrelated vaccine to shield people.
 
‘With mRNA vaccines and simple protein vaccines, we have seen some incredibly fast progress from having the sequence of a virus to getting a vaccine approved,’ he said.
 
‘Next time there’s a pandemic, I would hope that would happen in an even more smooth, streamlined manner because of our experience with COVID.’
 
However, he does not rule out the possibility altogether.
 
‘There would still be a period of few months, where potentially [the development of a vaccine] might not have happened yet.
 
‘Any other way to increase our immunity would be an advantage.’
 
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