People who are at risk of falling seriously ill with the flu could be identified by a genetic test and encouraged to have the seasonal vaccination, researchers say.

The NHS offers flu jabs for people who are known to be most in danger from the virus, including the over-65s, pregnant women, and those with underlying health problems, such as asthma.

But new research suggests that many more people in the general population are prone to suffer badly with the flu, and may even end up in hospital, because of their biological make-up.



About one in 400 people carries a variant of a gene called IFITM3 that makes them more likely to suffer serious illness when they are infected with the flu virus. The gene normally encodes a protein that helps the body’s cells resist viral infection, but this natural defence is impaired in people who carry the mutated version of the gene.



Paul Kellam, an expert in virus genomics at the Wellcome Trust Sanger Institute, told the British Science Festival in Bradford on Monday that the gene variant could help doctors spot people who are not usually considered a risk, but were genetically susceptible to the infection. “You can then start to stratify people ahead of time and prioritise them for vaccination,” he said.



The evidence for a link between IFITM3 and the severity of flu infections has grown over the past three years. The first indication came in 2012 when Kellam and others noticed that people hospitalised by the 2009 swine flu epidemic were more likely to carry the faulty IFITM3 gene variant.



The findings show that how poorly a person feels when they catch the flu is governed by their own biological make-up as well as the virus itself.



Kellam’s study prompted a flurry of further work by other scientists. Last month, a US-Chinese team pooled the results of four published studies to show that among 445 people infected with either swine flu or H5N1 bird flu, those with the IFITM3 variant were 24% more likely to have suffered a severe infection.



Prioritising people for the flu jab on the basis of their genetics could slash the number of cases of serious illness and save costs on hospital care. The 2009 flu epidemic in the UK killed more than 450 people.



The discovery of a gene variant that weakens people’s defences against the flu virus opens the door to new anti-viral drugs, said Kellam. Another study published last month showed that it might be possible to boost levels of the IFITM3 protein, and make people more resistant to the flu.



“The argument is that if you have a flu outbreak, you could raise general levels of defence. We’re not saying it would alter your risk of becoming infected in the first place, but the hope is that you do not end up with a serious, or life-threatening infection, and end up in A&E, or on a high dependency unit,” said Kellam.



In February this year, UK health officials announced that mutations in one of the main circulating strains of influenza had taken a toll on the seasonal flu vaccine. Doctors normally expect the vaccine to work in half of those who receive it, but evolution of the H3N2 strain of flu meant the number protected fell to just three in every 100 people.



Because IFITM3 is important for preventing a range of viruses from getting into cells, a treatment that boosts the gene’s activity in cells could offer some protection against other serious illnesses beyond the flu.



“By understanding genetic variants like this we can start to think about broad spectrum anti-virals that hit a whole range of viruses, from flu to dengue and Ebola,” Kellam said.

