Why is flu season worse this year?
Flu season came early this year and the NHS is bracing for what bosses say could be the toughest winter staff have ever faced. Here is all you need to know.
Thursday 4 December 2025 11:35, UK
Flu season has started unusually early this year, with the number of flu patients in hospital beds across England more than 50% higher than the same period in 2024.
An average of 1,717 patients were in hospital beds in England each day during the week commencing 24 November, including 69 in critical care - an increase of 56% for the same week in 2024, where the total was 1,098, with 39 in critical care.
The stark statistics come weeks after the NHS sent out a "flu jab SOS" to vulnerable people, as experts warned it could be its toughest ever winter.
So what's causing the flu surge, how bad could this winter be - and what role does the vaccine have to play?
What's causing the flu surge?
Experts believe a "drifted" strain of influenza A is responsible for flu season coming early this year.
They watched as Australia's flu season - regarded as a reliable indicator of what's in store for the UK - broke records for infection numbers, with warning signs also coming from the Asia-Pacific region, where Japan declared a flu epidemic in October and closed many schools.
There are three types of flu: influenza A(H1N1), influenza A(H3N2) and influenza B. This year, it's the H3N2 subtype that is prevalent.
Flu viruses are always evolving in a process known as antigenic drift, which is why flu vaccines are updated each season. In the Northern Hemisphere, the vaccine strains are selected in February ahead of the following winter.
But this strain of H3N2, specifically referred to as subclade K, evolved more than usual over the summer, making it quite different from the vaccine strain, according to the UK Health Security Agency (UKHSA).
After the release of the latest NHS statistics, Sarah Woolnough, chief executive of The King's Fund health think tank, warned that the flu season had "yet to peak" and that it was "too soon to know how long this surge will be sustained for".
How bad is it?
Experts have warned thousands of people could die this winter - after flu deaths more than doubled last year.
The UKHSA estimates 7,757 people in England died from flu last winter compared to 3,555 the year before. Child deaths involving flu also increased from 34 to 53.
NHS bosses have warned they expect an incredibly difficult winter.
In November, chief executive of NHS England Jim Mackey said it will be "one of the toughest our staff have ever faced".
"Since stepping into this role, the thought of a long, drawn-out flu season has kept me awake at night. And, unfortunately, it looks like that fear is becoming reality."
He added: "Australia has just endured its worst flu season on record - over 410 000 cases - and all the signs suggest the NHS will face similar challenges in the months ahead. From December through to March our hospitals will be at capacity."
How effective are the vaccines?
The UKHSA has assessed how well this season's vaccine is working by studying whether people who have been vaccinated are less likely to attend hospital with influenza.
It has found that the vaccine is currently 70-75% effective at preventing hospital attendance in children aged two to 17 and 30-40% effective in adults.
Dr Jamie Lopez Bernal, consultant epidemiologist for immunisation at UKHSA said he is "confident" that whatever strain circulates, the vaccine will still help protect those most vulnerable.
He added that good respiratory hygiene and minimising contact with others if you are displaying symptoms can also help to prevent the transmission of flu.
The NHS delivered 14.4 million flu vaccines in the autumn - over 160,000 more than at the same point last year, according to the latest figures from NHS England.
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Should you get a flu vaccine?
Flu jabs are free and recommended for the following people:
• Everyone aged 65 and over
• Those under 65 in clinical risk groups
• Care home residents and carers
• Pregnant women
• Close contacts of those who are immunosuppressed
• Frontline health and social care workers
• Children
Jabs started being given out in October, but if you haven't had yours yet, the NHS offers them until 31 March.
If you're eligible, you can get one by:
• Contacting your GP surgery to book an appointment
• Booking a free NHS flu vaccination appointment at a pharmacy online or in the NHS app
• Finding a pharmacy that offers free NHS flu vaccination where you can walk-in and get vaccinated without an appointment (if you're aged 18 or over).
According to the UKHSA, as of 23 November, 69.6% of all those aged over 65 years were vaccinated, but the uptake was lower among those aged under 65 with long term health conditions (35.1%), pregnant women (33.9%), children aged two years (39.8%) and in children aged three (40.3%).