Four giant lorries pull into the loading bays at Seqirus’s vaccine plant in Liverpool every morning like clockwork. On board, a precious cargo — 575,000 chicken eggs in which lie the seasonal safety of the nation.
This daily delivery is the crucial first step in creating the flu vaccine that will protect the public and stop the NHS being overwhelmed by influenza and Covid-19 — and the Mail is the first to see the inside of the factory at the centre of it all.
This winter threatens to be the worst flu season in recent years, with up to 60,000 deaths predicted as reduced flu immunity and a potential Covid third wave could derail an already weakened health service.
Professor Jonathan Van-Tam, England’s Deputy Chief Medical Officer, warned this week that flu poses a ‘significant health risk’ as it will be circulating with Covid-19 at the same time the cold weather causes an increase of people mixing indoors.
The eggs are washed, sorted and incubated in a series of 37 rooms, each housing 172,000 fertilised eggs. They are kept in strictly controlled conditions for 11 days in order to create the perfect environment for a virus to be reproduced. The eggs are stored on racks that change their angle of tilt every hour and stay at a precise temperature of 37.5c (99.5f) and 65 per cent humidity — the ideal conditions to develop their embryos
The eggs are then ready for the production line, which scans 132 eggs at a time and rejects those that are infertile — 45,000 a day — before being jabbed with a needle with 0.2 ml of ‘working seed’, a solution that contains the active flu virus, which has been cultured in laboratories. After this, the influenza virus begins multiplying within the shell
Imperfections are prevented throughout the process by randomly examining the eggs in a process called ‘candling’, in which experts use ultraviolet probes to check whether or not an egg is still fertile. Infertile eggs are discarded as they are discovered
After being incubated for 72 hours, the eggs are ‘blast chilled’ to make sure that the embryo stops growing. The virus-filled eggs now join a harvest line, where a huge machine uses a blade to slice off the top of each eggshell. Probes extract some of the clear liquid from inside the egg, known as allantoic fluid — which now contains thousands of copies of the influenza virus
Salvation comes in a small syringe containing 0.5 ml of vaccine that starts its journey to the patient at an 18-acre plant in a hinterland of factories and warehouses in south Liverpool.
At peak production, it has 6.1 million eggs at various stages of vaccine development, with its 650 staff working round the clock on the flu front line.
Fertilised chicken eggs are an ideal medium to grow the strains of viruses that are the vital components of an effective vaccine.
At the Seqirus plant, they have finessed production to such a level that it will despatch up to 30 million doses this year to immunise the UK.
All over-65s receive egg-based vaccines as they can carry the adjuvant that promotes a better immune response. Vegans, however, are able to ask for cell-generated jabs.
‘The scale is astounding,’ says Alan Collins, primary incubation unit process leader.
‘Every part of the process has to work perfectly to ensure we can supply enough vaccine to keep the nation safe. It is a complex and demanding production line but I enjoy coming to work every day because we are helping to protect lives.’
Seqirus has recently invested £50 million in production facilities and taken on 120 new staff.
The virus is then deactivated using formaldehyde and the solution is purified with a centrifuge. The solution remaining contains the virus antigen. This triggers a human immune response to the infection without causing illness. Seqirus produces four strains of the virus, identified by the World Health Organisation in February, and mixes them to form a quadrivalent vaccine (above) to protect patients against the four different strains of the flu virus
The complete vaccine solution is collected in giant 500 litre sacks. This sterile machine then fills syringes at high speeds
The solution is measured and put into 0.5 ml syringes before the vaccine batches are thoroughly checked by workers at the production facility
The final product is distributed to doctors and pharmacists across the country
‘We are quality-controlled at every stage,’ says John Riley, formulation process leader.
‘Each 500-litre batch we produce contains 900,000 vaccines, so that is 900,000 lives we are protecting and we don’t want anything going wrong.’
Raja Rajaram, head of medical affairs at Seqirus, adds: ‘This is an important flu season and uptake of the vaccine will be critical in ensuring the NHS is not overwhelmed this winter.
‘We had virtually no flu last year — but now we have been released from the lockdowns, we are mixing more freely with people going back to offices and starting to travel. The vaccine will have a huge role to play in reducing the burden on the NHS.’
The flu vaccine can be given at the same time as a Covid booster jab.
Public Health England is aiming to beat its record of 80.9 per cent coverage of the over-65s from last winter to 85 per cent this season as part of the UK’s largest ever flu immunisation programme.
The jab is also being offered to the over-50s and to younger children.
Millions will receive their injections this month when the flu season starts — but many will not know that the flu jab programme owes its success to the humble egg.