The Government is "worried" about the number of people who are not vaccinated against the flu, Minister for Culture, Communications and Sport Patrick O'Donovan has said.
It comes as the HSE said the Health Protection Surveillance Centre is observing a higher number of notified influenza cases and notified hospitalised influenza cases than the same week in previous seasons, since influenza was made a notifiable disease in 2004.
In a statement, it said that the HPSC is seeing earlier flu activity here than in recent seasons.
Almost 3,000 cases of flu were recorded last week.
The HPSC has said that 2,944 cases were recorded in the week starting 30 November - an increase of 49% on the previous week, when 1,971 cases were recorded.
Hospitalisations increased by 58%, from 415 cases to 657 cases.
Emergency Department (non-hospitalised) influenza cases increased by 55%, on the previous week to 1,662.
The HPSC report shows flu cases at high levels overall and highest in those aged under 15 and over 80 years of age.
It said there have been 42 intensive care unit admissions, while 13 deaths have been reported for this season to date.
Speaking during Leader’s Questions, Minister O'Donovan said: "We’re worried about the amount of people that could still get the flu vaccine.
"Well over three-quarters of the people in hospital at the moment with the flu aren’t vaccinated, that’s a concern."
He was responding to a question from Labour’s Conor Sheehan, who described the low uptake as "frightening" and said the Government had "failed" to address this with information and awareness campaigns.
He said the vaccine should be free and universal, and the Labour Party has been "saying this for ten years".
He also said reports that an "enhanced" flu vaccine was not obtained because of cost reasons was "incredibly concerning".
He said: "We know the enhanced flu vaccine outperforms the standard vaccine, particularly with older people, and this is madness, given the data we have from Australia."
Australia's flu season comes before Ireland’s and data from strains in circulation there informs the development of vaccines for the northern hemisphere.
Mr O'Donovan described the vaccine as "the best form of protection" and encouraged "anybody that still hasn’t got the flu vaccine to please go out and get it".
He said he was vaccinated himself as he is "from a cohort of people where I’m immunosuppressed, I need to get it".
In Ireland the vaccine is free for a number of groups including everyone over 60, children aged between two and seventeen, people with underlying medical conditions, healthcare workers and carers and pregnant women.
The HSE said: "The vaccine available this year provides strong protection against serious illness, and we would urge all eligible people to take it up as soon as possible."
Visiting restrictions at Letterkenny hospital
Meanwhile, Letterkenny University Hospital has appealed that people who may have flu like symptoms not to visit the hospital.
As part of efforts to combat further spread of the flu, infection control measures and visiting restrictions have been introduced at the hospital.
Among them is that no person should visit the hospital if they are symptomatic with respiratory illness until after having no symptoms for 48 hours.
Patients can have a maximum of two visitors, unless there is a pre-approved exception.
The hospital has also said that there should be no visits by children, apart from the maternity ward where children can only visit with prior approval.
In a statement, Letterkenny University Hospital said that 18 patients are being treated with the flu and that there are a "particularly high" number of people attending the hospital's emergency department with flu symptoms.
It said that 153 people were hospitalised in Donegal since the start of this year's flu season, including 53 last week.
