WILL VACCINES PROTECT MY CHILD AGAINST 'K STRAIN' OF FLU?
Concerns have been raised about whether vaccines are effective in protecting children and the elderly against the rampant “K strain” as Britain faces the worst flu season on record.
Health officials are playing catch-up on vaccinations, as not enough people have come forward for an immunisation appointment.
The ‘K strain’ is driving the “tidal wave” of flu cases, with the virus’s mutations causing more people than normal to become ill, and increasing pressure on hospitals. Flu outbreaks in care homes are also becoming more frequent.
Children have been hit hard, and four million of them – more than half of those aged between two and 17 – remain unvaccinated.
However, the best defence against catching the flu is the vaccine, scientists say, which is worth getting as it provides some, if not full, protection.
What is the flu vaccine and what is in it?
The flu vaccine is offered on the NHS to everyone over 65, pregnant women, people living in a care home, those with long-term health conditions, carers, the immunosuppressed, and schoolchildren, among others.
The reason so many people are being offered the chance to receive the vaccine for free is because flu can be a particularly dangerous infection to catch for those with weak immune systems or those who have never previously had it.
With so many different people at risk of catching and falling ill from flu, the Government has a range of seven different vaccines available. The specific vaccine a person receives depends on their age, health and whether they suffer from any allergies.
Children, for example, get a nasal spray vaccine which shoots live, but weakened, flu up the nose. This is an AstraZeneca vaccine, which has been used for more than a decade in school vaccination programmes and launches every year from Sept 1.
However, all the vaccines contain fundamentally the same thing. In each dose there are three different vaccine strains which each tackle a different type of flu.
One is for influenza B, which is at very low levels this year, and two are for different types of influenza A – H1N1 and H3N2. ‘K strain’ is a mutant form of the latter, and the first H3 flu season in the UK since 2022.
Scientists meet up twice a year to talk about the flu vaccine and decide if it needs updating. The current product was decided upon in February at a WHO meeting at the Crick Institute in London.
This process requires trying to predict the future because the experts have to essentially guess which strains of flu will be the most common in six months’ time.
The version of H3N2 they decided should be in the vaccine this year is based on a strain from 2023.
Subclade K, which makes up 78 per cent of flu cases so far this winter, did not exist at that time and emerged in Australia in the summer as a result of “genetic drift” and nine new mutations.
As a result, scientists have found there to be a “mismatch” between the contents of the flu jab and that of the main strain of flu causing sickness.
How good is it?
Scientists are investigating how good the flu vaccine is against the K strain as a result of the vaccine being a suboptimal match.
The answer, they think, is good enough, and they are urging as many people to get the protection it offers as quickly as possible.
Data from a study published by the UKHSA found early signs that the 2025 winter flu jab provides the same level of protection as in a normal year.
The vaccine has an effectiveness of 75 per cent, meaning a vaccinated child is about 75 per cent less likely to end up in A&E or hospital with flu compared with an unvaccinated child.
However, vaccine effectiveness dropped to 60 per cent for adults between 18 and 64, and 35 per cent for over-65s.
Even in older people, where the vaccine has the smallest impact, people who get vaccinated are a third less likely to go to hospital than those who are unvaccinated.
These figures are within the “typical range” for what the flu jab normally offers, scientists say. All the different vaccines the UK uses provide comparable protection, government officials believe.
Should I bother getting it now?
How long the vaccine lasts remains unknown, but a recent study from the UKHSA on last year’s flu season found protection begins to wane after nine weeks.
Around 17.4 million people had been vaccinated as of Dec 7, the latest available data from the NHS show.
More than seven million of those doses were given out in the first two weeks of October – coinciding with when all over-65s can come forward for their jab.
Over-65s are the most vulnerable to flu, and are also the cohort with perennially highest vaccine uptake figures, at around 60 per cent.
This suggests that there was a rush among older people to get the flu jab at the start of the window in October. Those jabs will now, perhaps, be starting to lose their potency.
UKHSA data also shows that outbreaks in care homes are on the rise. There were 248 outbreaks in the last week, and 160 of them came at care homes, with the majority caused by flu.
Government scientists actually suggested that adults could be better off waiting to get their vaccine to time it for when the flu wave is expected to hit.
With infections rising and the NHS under increasing strain from what it is calling a “tidal wave” of flu cases, now is perhaps the perfect time to get vaccinated as it will offer protection over Christmas, when people are mingling more.
Data from the NHS shows that over-55s are now seeing a spike in flu cases going to intensive care, and data coming out of Australia indicates this flu season may be longer than expected.
With a flu season that may have a longer than usual tail, getting vaccinated for the coming months is advisable.
Should children get the vaccine?
More than 3.6 million school-aged children have had the flu vaccine, with another half a million two and three-year-olds also getting the vaccine.
Schoolchildren get a nasal spray because, the NHS says, it is “painless and easy” and has an excellent safety profile.
It also seemingly has the ability to provide “cross-protective immunity”. With live viruses the vaccine produces a very broad response in the body, scientists say. This means that, even if the vaccine is made with a mismatched strain, it can cause the body to protect itself to some extent. This could be part of the reason children have the highest vaccine effectiveness results, a UKHSA study found.
“The apparent cross-protection against drifted viruses may be a result of the breadth of the immune response provided by [nasal spray vaccine],” the UKHSA scientists write in a paper, published in Eurosurveillance.
Schoolchildren respond well to the vaccine. Those aged between five and 14 are the most likely to be sick with flu, data shows, followed by 15 to 24-year-olds.
However, flu vaccination rates among children tend to be low, with only half of the eligible children receiving the vaccine last year.
The vaccine can also protect vulnerable people around the children, hence the advice to get youngsters vaccinated to protect their grandparents. Older people make up fewer cases, but more of the hospital admissions.
2025-12-12T16:30:31Z
