The future of the flu

A “universal flu vaccine” that could prevent deadly future pandemics is on the horizon following a major breakthrough by scientists.

In an article in Science, the team behind a vaccine developed at the University of Pennsylvania announced that it had been found to induce antibody responses against all 20 known subtypes of influenza in mice and ferrets. If the vaccine also works in humans, “flu pandemics, in effect, would be defanged”, wrote Helen Branswell at health news site Stat.

How great is the current flu threat?

Countries worldwide are facing flu outbreaks following a lull in infections during Covid-19 lockdowns. Hospital admissions for flu in England this week overtook Covid admissions for the first time since the coronavirus pandemic began.

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In fact, said Sky News, latest figures from the UK Health Security Agency (UKHSA) “show flu admissions are running at a higher rate than in any week during the past four winters”.

UKHSA consultant epidemiologist Dr Conall Watson warned that “flu is now circulating widely” and that medics were“ expecting case numbers to continue increasing as we move further into winter”.

Amid fears of a major flu pandemic, experts are currently pinning their hopes on existing vaccines. Each year the virus mutates to produce new flu strains from the 20 know subtypes, and existing vaccines target three or four of the strains already “circulating in the human population”, said Nature.

The effectiveness of these vaccines varies wildly, however. In a good year, the vaccine is 60% effective, but “some years, effectiveness plunges to as low as 10%”, wrote Science’s Jon Cohen. All the same, some protection is “better than nothing”, Michael Osterholm, an epidemiologist at the University of Minnesota, told the site.

What’s special about this universal vaccine?

A universal flu vaccine would not “replace the need for an annual flu shot”, said Branswell on Stat, and nor would it “block all flu infections”. But a universal vaccine would protect against a flu pandemic.

Guidance from the UK government on pandemic flu explained that these major outbreaks occur when a novel influenza virus that is “markedly different” from other strains emerges. Because these viruses are new, immunity levels are low or non-existent.

The world has faced four flu pandemics over the last 100 years or so. The most recent was in 2009, when the H1N1 swine flu killed up to 575,000 people. By far the most deadly was in 1918, when the so-called “Spanish flu” infected around a third of the global population and killed an estimated 50m people.

The UK government has been warning in recent years that another flu pandemic is “likely” and may be “one of the most severe natural challenges” the UK will face.

Scientists have been working for years to create a universal flu vaccine in order to prevent a deadly outbreak. A vaccine that could “prime the immune system to better respond to new flu viruses”, said Branswell at Stat, could significantly lower “the risk of hospitalisation, death and social disruption”.

What challenges remain?

The Pennsylvania University team’s vaccine is based on the same mRNA technology used in the Covid-19 jabs from Moderna and Pfizer, and experts are hoping that it may prove equally effective.

In tests on mice and ferrets, “the animals generated antibodies specific to all 20 strains of the flu virus”, New Scientist reported, “and these antibodies remained at a stable level for up to four months”. Peter Palese, a microbiologist at the Icahn School of Medicine at New York’s Mount Sinai hospital, told the site that mice and ferrets “are as good as animal models get” and that the test results were “a good indication of what will happen in humans”.

Stat’s Branswell warned that there were still there were “significant hurdles ahead”, however. Like Covid vaccines, the mRNA-based flu vaccine may “trigger uncomfortable side effects in a significant portion of people,” she wrote. “Finding a dose that would induce enough protection in people against all 20 targets while still being tolerable to take will be a challenge.”

And “figuring out a way to get regulatory approval will also be a substantial challenge”, Branswell added.

Alyson Kelvin, a vaccinologist at the University of Saskatchewan in Canada, told The New York Times that the next step would be to test the vaccines on monkeys and people. But as she pointed out, new vaccines have to be proven to prevent a certain portion of infections, and “how do you evaluate and regulate a vaccine where their targets aren’t circulating, and so you can’t really show effectiveness?”

On a positive note, said New Scientist, mRNA vaccines “can easily be scaled up compared with other approaches”.

Supposing all other hurdles were cleared, the new universal flu vaccine could potentially be ready within two years, professor John Oxford, a virologist at Queen Mary University in London, told the BBC’s Radio 4 Today programme. Oxford “said the jab could save thousands of lives”, The Independent reported.

The vaccine represents a major “breakthrough”, he added, and “the potential is huge”.