Flu season in Ireland this winter will be “challenging” and will also peak two weeks earlier than normal with the biggest surge in hospitalisations expected around Christmas time, the Health Service Executive (HSE) has said.
The number of people admitted as inpatients in hospitals due to influenza has doubled in a week, with 418 hospitalisations recorded during the last week of November, compared with 213 the previous week.
Dr Colm Henry, chief clinical officer of the HSE, said the influenza season has come to Ireland earlier than normal and will be at least as challenging as it was last year, which was a season that recorded particularly high numbers of flu infections.
Dr Henry said the weekly hospitalised numbers would peak at somewhere between 750 and 1,500 inpatients who have influenza, with the peak expected on Christmas week or in the first week of January.
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He said the HSE had been tracking the flu season in the UK and, earlier this year, in the southern hemisphere, and knew that it was going to peak early.
He said the range of possible hospitalisations was hard to predict with accuracy because there was still much to play for in keeping the numbers down, including vaccination, control measures for infection prevention in hospitals and other levers to manage outbreaks.
The comparable figure for this week in 2024 was 73 hospitalisations but the season did not peak until the second week of January, where there were just over 800 hospitalisations. The number of hospitalisations is expected to match that this winter, or perhaps exceed the 2024 figures.
The higher numbers have been attributed by some to a mutated version of the virus which is spreading.
Dr Cillian de Gascún, director of the National Virus Reference Laboratory said on Friday there was no evidence as yet that the mutated version, Influenza A (H3N2) subclade K, causes more severe disease or is more transmissible. He said that because viruses have continued to evolve, the efficacy of vaccines produced before those genome changes happened might be consequently reduced. He said the antibodies produced by the vaccines might not bind as well to the influenza.
“However, the vaccine is still the best means of protection we have, and – even with the antigenic drift [or viral mutation] – would be expected to provide protection against severe disease,” said Dr de Gascún.
The highest circulation has been in children aged from five to 14 years with hospitalisations rising, mostly for adults 65 years and older.
As of November 23rd, more than half of all adults over 60 had received a flu vaccine. However, the figure was less than 20 per cent for children aged two to 17. Moreover, only a quarter of HSE healthcare staff have been recorded as taking the vaccine.
Dr Henry said influenza can trend to a more severe illness in older people and urged people to get vaccinated.
“The fact is that it’s not just a person protecting themselves, which is the primary appeal to people, but they are also protecting somebody who’s more vulnerable than they are, in other words somebody who may be vulnerable to getting severe disease,” he said.
Minister for Health Jennifer Carroll MacNeill said the experience from the southern hemisphere was of a particularly bad flu season in 2025.
“Vaccination generally serves to reduce transmission, and that’s really important, and particularly going into Christmas, as people are going to be mixing more and more,” Ms Carroll MacNeill said.
