A leading official in the HSE says medical staff not getting the flu vaccine can lead to outbreaks in hospitals.
Latest figures show that 28 people have died as a result of the flu so far this season, up from 22 on this day last week.
It also comes as hospitals have this week seen the highest numbers waiting on trolleys since records began.
Around half of hospital staff got the flu vaccine this season.
However, the HSE's Dr Kevin Kelleher said the take-up of the vaccine needs to be higher.
He said: "If nobody was being vaccinated in hospitals, flu would fly around hospitals massively.
"By the very nature of getting staff vaccinated, that reduces the chance for flu to get transmitted around the hospitals.
"The more we get people to be vaccinated, the better it will be within our system."
Meanwhile, Dr Kelleher also warned that the number of deaths as a result of the flu will continue to rise as the flu season continues in the coming days and weeks.
He observed: "We've had 28 deaths explicitly recorded... they will grow and grow because they happen after people have been admitted to hospital.
"That will carry on growing, and we will still see some of those when I've said officially that the season is over."