Health professionals must encourage more people to get flu vaccinations, the Health Protection Agency (HPA) has said.
The warning comes after the HPA released figures showing that last year's outbreak led to 602 deaths in the UK, while just 50% of people in at-risk groups were immunised against flu in England and Wales.
Older people are usually the most vulnerable to flu. However, last year, 70% of the deaths were people 15 to 64-year-olds. This was because swine flu, which those from higher age groups have some resistance to, was the main strain.
Officials said they were concerned about the vaccination uptake figures.
Scotland fared somewhat better, with a 57.4% uptake among at-risk people under the age of 65 and 74.5% of people over 65.
The flu vaccination programme encountered a number of problems last year with some GPs reported to have run out of jabs. Leftover vaccines from the pandemic of two years ago were given to some people last year but these did not protect against all the strains in circulation.
The government has now given the NHS in England a target to raise uptake to 75% over three years.
"More advice on television every few hours from September to December when surgeries are vaccinating, the health message is not getting through and primary care practitioners cannot do it all, more media involvement is needed. What about posters in hospital outpatient clinics, podiatry clinics, diabetic clinics etc etc. Where are these? We are trying our best in primary care but it should be a primary and secondary care initiative" - Barbara Norris, South Wales
"Publish this info as posters and include retail services, only about £10" - Una Duffy, Surrey
"I contracted swine flue in January 2011, I was in intensive care for nearly seven weeks! My recovery has many complications. If it was not for the amazing care and treatments given to me by the Cardiff NHS I would not be here now and recovering at home after 12-week stay in hospital. I will ask for a jab when available. Sadly some are still in hospital and recovering" - Michael Boniface, South Wales
"Older people need education! I am 'at risk' and always have the jab. Comments of people in my age group, 65 are frightening. 'You will get flu now', 'You will be ill for months'. Where does this come from? Education, education!" - Frederick Whiting, Somerset