UK stockpiling bird flu vaccines for humans as outbreak fears increase

The UK Government is ordering tens of thousands of doses of a vaccine to protect people in the event of an outbreak of bird flu in the human population, i can reveal.

A contract to supply an influenza vaccine to offer immunity against the deadly H5N1 virus has been put out to tender by the UK Health Security Agency, to be held in stockpile in case of an outbreak.

It would be ready for use from this December “in the event of zoonotic infections and for use in response to the entry of H5 influenza into the UK population”, the tender says.

The risk of bird flu to humans is still classed as “low”, as it cannot currently transmit between people.

However, the move marks a stepping-up of readiness for a possible new pandemic if the virus makes the genetic leap to human-to-human transmission.

Fears of bird flu spilling over into humans have been heightened following an outbreak in cattle herds in the US.

There have been cases of bird flu in some mammals, such as sea lions and mink, but the outbreak in US dairy farms is the first large-scale instance where animals that are in regular contact with humans had contracted the virus.

It is also possible that UK poultry workers and others who work closely with birds would receive the vaccine as a routine to prevent them contracting the virus.

Supplies of the vaccine would be in place initially for a year, the contract tender says.

Earlier this month, the European Commission signeda deal for 40m doses of a bird flu vaccine for use by EU countries earlier this month and was made following public health and commercial advice to the UK government, i understands.

This week, Finland announced it would be the first country to administer bird flu vaccines to people. Farm workers will receive two shots of the jab from next week.

While the current strain of H5N1 has been circulating in global bird populations since late 2021, governments around the world, including the UK, have stepped up their risk assessments in the wake of the US outbreak in cows.

So far this year, 11 people have been infected globally with bird flu. In nearly all cases they were in close contact with poultry or wild birds at the time of infection. There have been two human cases of bird flu connected to the US cattle outbreak.

Earlier this month a farm worker in Mexico died from bird flu, although this was from a different strain, H5N2.

This was the first human with a lab-confirmed case of H5N2 to have died, according to the World Health Organisation. The 59-year-old had been in hospital in Mexico City and died on 24 April after developing a fever, shortness of breath, diarrhoea, nausea and general discomfort, the WHO said.

The government’s latest assessment of avian influenza says the risk of bird flu to the human population may have risen from level 3, where there is transmission between mammals that is either limited or driven by intensive farming, such as in the case of mink, to level 4, under which there is “sustained and/or multispecies mammalian outbreaks; increasing human zoonotic cases or limited person-to-person spread, linked to zoonotic exposures”.

How worried should we be about bird flu?

The stockpiling of bird flu vaccines by the UK – and similar moves by European Union countries – will raise fears of another pandemic from a potentially deadly virus. So how worried should we be?

So far, there have been only a handful of cases in people, with a relatively high death rate, but they were all infected by direct contact with birds and did not pass the virus on to others. The overall risk to humans is classed as low.

Yet while the H5N1 strain of avian influenza has been circulating among poultry and wild birds globally since autumn 2021, two key developments in the past year have caused concern among scientists that it could at some point evolve to transmit between people.

The first of these was in 2023, when outbreaks began to emerge among mammals, both in captivity – such as farmed mink – and in the wild, including sea lions in South America.

While these animals would have been infected by birds close by, there was some evidence that the virus was spreading between the mammals. If this so-called mammalian adaptation could occur, scientists were concerned that a further evolution, to spread between humans, could take place.

The second development was earlier this year, when cows in dairy herds in the US began to develop infections. The outbreak has spread to 12 US states to date.

While there is a very low risk from US dairy produce – as the virus is believed to be killed by pasteurisation – the exposure of farm workers and cattle herders has raised fears about a spillover event to humans, something which was not a concern in the sea lions outbreak.

It is this outbreak which has caused the UK to raise its threat level from bird flu from 3, meaning limited transmission between mammals, to a likely level 4, with more widespread mammalian transmission, although this is still low confidence.

The UK government agency risk assessment still classes a level 5 event – outbreaks among humans not linked to contact with infected birds or animals – as between highly unlikely (10-20 per cent) and unlikely (25-35 per cent).

And we are still a long way off from level 6 – when there would be sustained human-to-human transmission, and the government would have to make official public health announcements to the population.

The good news is that, unlike when Covid first emerged, there are already vaccines in production that are tailored to the H5 group of influenza viruses, so if level 5 were reached in the UK, jabs would be rolled out quickly.

This raising of the risk level is low confidence, however. Level 5 would see outbreaks of the virus in humans on a larger scale and not linked to close contact with birds or animals, while level 6 would mean sustained human-to-human transmission, and would trigger major announcements by government ministers and scientists about vaccine use and public health precautions.

The assessment was compiled by scientists at the UKHSA, the Animal and Plant Health Agency, and the Department
for Environment Food & Rural Affairs (Defra).

Despite fears of a fresh pandemic, the key difference with the emergence of Covid is H5 vaccines are already in production that could be used to target H5N1 in the event of sustained infections among people.

The UK risk assessment says there is a 10 to 20 per cent chance (highly unlikely) that UK cattle will be infected with the same strain as the US outbreak within the next six months.

Over the same time period, there is a remote chance – less than 5 per cent – of human infection resulting from exposure via legal importation of unpasteurised dairy products.

In the highly unlikely event UK cattle are infected, there is a 50 per cent chance that one or more humans will be infected, the risk assessment says.

It adds: “The baseline risk of influenza A(H5N1) evolving to cause human transmission before the current cattle outbreak was previously considered to be remote chance (0-5%). There is consensus that this risk has now increased.

“However, with current limited information we cannot resolve the risk further and it may fall at highly unlikely (10-20%) or unlikely (25-35%).”

An announcement of the vaccines contract is due to be made after the tender closes next month.

The Department of Health and UKHSA were unable to comment due to election purdah rules.