The flu jab may fail to protect people this winter, vaccine makers fear, because global Covid surveillance prevented laboratories gathering sufficient data on the dominant variants.
Health experts were already concerned that coronavirus restrictions had left people with little natural immunity to influenza, but now they fear the vaccine may also be mismatched to the circulating virus.
The World Health Organisation (WHO) made the recommendation about what to put in northern hemisphere jabs in late February, but vaccine makers say that global genetic sequencing of flu had dropped by up to 94 per cent in the months preceding the decision.
The mass cancellation of flights, as countries closed their borders and imposed travel restrictions, has also led to a 62 per cent drop in shipments of influenza surveillance samples, experts warn.
There are fears that a mismatched flu vaccine, coupled with waning immunity, high levels of Covid and the NHS backlog, could quickly lead to the health service being overwhelmed this winter.
Dr Beverly Taylor, Head of Influenza Scientific Affairs and WHO lead, at vaccine maker Seqirus, which provides Britain with seasonal flu jabs, said: “We saw quite a big reduction in the labs supplying the genetic sequence data to WHO, and around September last year, we saw a 94 per cent drop in the genetic sequence data that was reported into the database. So this has had a massive impact in the reporting.
“We could have reduced the opportunity to identify viruses as they emerge. We certainly have reduced the opportunity to look at which viruses would give the best overall protection and the best coverage of all the circulating viruses.
“What we’re actually seeing is influenza in geographical pockets, so it’s very difficult for us to tell which one is going to be the winner. We could potentially see a mismatch for at least one of the subtypes. And so that’s cause for concern.
“This winter, it’s going to be over 18 months since most of us have seen influenza and there is concern that we’ll see a lower level of population immunity.”
Potential surge in respiratory viruses this winter
Global influenza surveillance has been conducted through WHO’s Global Influenza Surveillance and Response System since 1952. But the pandemic meant that many labs have been repurposed to sequence Covid data, raising the risk of a mismatch.
In 2015, a mismatched flu jab contributed to the largest spike in mortality in a generation, when 28,189 excess deaths were recorded, leading to a fall in life expectancy in England and Wales for the first time in two decades.
That year, the jab was found to work in just one in three adults, compared with the 50 to 70 per cent that it usually protects.
The Academy of Medical Sciences said a potential surge in respiratory viruses this winter could push the NHS to breaking point, and warned that between 15,000 and 60,000 people could die of flu this winter. A recent report from the academy warned that a mismatch could make the situation worse.
“In years with mismatch, (vaccine) effectiveness against both infection and severe disease can be markedly reduced, resulting in more severe epidemics,” the authors wrote.
“Given the global decrease in influenza circulation, there has been much less information available on which to base predictions about which influenza strains will circulate this winter.
“As such, there is an increased likelihood that there will be influenza vaccine mismatch this winter, which could result in more infections and disease.”
Experts said last winter saw the biggest uptake of flu vaccine in Britain ever recorded, which was ‘good news’ but they said they were concerned that ‘vaccine fatigue’ may see fewer people take up the offer this winter.