The flu virus is "actively circulating" but has not yet reached its peak - with 15 patients admitted to critical care units suffering a life-threatening condition so far this winter.
An HSE spokeswoman confirmed that seven people died from the virus during the period from December 5 to January 1.
Medical experts warned that the number of influenza-related calls to GP out-of-hours services had now reached the highest rate since the winter of 2010-2011.
Older people are at greatest risk of contracting the predominant flu strain, AH3.
Latest figures show 270 people have been hospitalised so far this winter - the majority aged 65 or older.
According to the Health Protection Surveillance Centre (HPSC), 15 patients have been admitted to critical care units this season to date.
Those with flu symptoms and bad colds have been urged to get vaccinated as soon as possible, as influenza rates doubled last week and are expected to rise still further.
The health service has previously warned that a particularly strain of the flu virus could cause up to 1,000 deaths if Ireland has a severe winter.
Flu is an infectious acute respiratory condition that in certain instances can be life threatening, especially for those suffering a long-term illness or some pregnant women.
HSE specialist in public health medicine Dr John Cuddihy urged these in high-risk groups to get the vaccine as soon as possible, warning that the flu season had not yet reached its peak.
"There is a new vaccine every year, the constituents of which vary," he said.
"Influenza can be life threatening, so it is important to get vaccinated."
It can take two weeks for the vaccine to 'set in', he added, and stressed those in at-risk groups were most vulnerable.
"It is not too late for this winter," he said. "It can be difficult to tell when a particular strain has peaked, but it has not happened so far on this occasion.
"Each year we have seasonal influenza, starting in late autumn. It occurs in countries around the world so it's difficult to pinpoint where the first case was in Ireland."
Ann Marie Horan, a pharmacist who is a member of the executive committee of the Irish Pharmacy Union, said vaccination was the best way to reduce the chances of contracting the flu virus and spreading it to others.
"We would especially encourage at-risk patients, elderly people, pregnant women and those with a chronic illness, to visit their local pharmacy and get the vaccine now," she said.
Symptoms of flu come on very quickly and sufferers will experience severe muscle aches and a high fever.