The Health Service Executive has said it is "finalising an operational plan" for the administration of Covid-19 booster vaccines to healthcare workers.
Following the recommendation from NIAC, the HSE said it expects to start administering the doses to workers "within the next week".
It said: "As with other cohorts, the booster dose should be given six months following completion of the primary vaccination schedule."
The HSE also said it is "progressing well" with the vaccination of a third primary dose for immunocompromised people and booster doses for long-term care residents over 65 and people aged over 80.
"As of yesterday, over 73,000 immunocompromised people have been identified.
"Over 43,000 have already received their third primary dose, with over 155,000 booster doses administered."
Around 270,000 frontline health staff are due receive the booster vaccines.
The advice from NIAC is that if a healthcare worker has had a laboratory confirmed Covid-19 infection, after a completed primary vaccine course, the booster dose should be delayed for at least six months after the Covid-19 infection was diagnosed.
There have been more than 28,900 Covid-19 cases in health staff recorded.
The National Immunsiation Advisory Committee has said that the greatest risk of transmission of Covid-19 in healthcare facilities is from people who are not vaccinated.
It also said booster doses have not shown any unexpected short-term safety concerns.
NIAC said a booster dose of Covid-19 vaccine increases neutralising antibodies, which are important for protection against infection.
Booster doses have also been shown to reduce breakthrough infections.
In its overview of recommending booster vaccines to health staff, NIAC said health staff with breakthrough infections can unwittingly be a source of hospital or residential outbreaks, involving both patients and other healthcare workers.
It said healthcare workers accounted for less than 5% of confirmed cases of Covid-19 reported between 15-28 October last.
NIAC said booster vaccines do not immediately contribute to outbreak management, or take the place of public health and social measures.
It said the risk of myocarditis (inflammation of the heart muscle), or other rare adverse events following an mRNA booster dose, has yet to be characterised and will be closely monitored.
The Tánaiste has said he believes the Government will seek advice from the National Immunisation Advisory Committee (NIAC) to extend the vaccine booster programme "more widely".
Minister for Health Stephen Donnelly said the issue of booster shots for people under 60 will be kept under review but at this stage there are no plans to offer boosters to the general population.
NIAC has already approved booster shots for people who are over 60, healthcare workers and those who are immunocompromised.
During Leaders' Questions in the Dáil, Leo Varadkar said that he believes an extensive vaccination programme will be needed.
He was responding to the Labour leader, who told the Dáil that health workers are exhausted and are facing a "perfect storm" this winter due to the pandemic but also other illnesses such as the flu.
Alan Kelly said workers rallied last year, but he fears they do not have it in them this year.
The Tipperary TD called for the publication of the winter plan and for serial testing for nursing homes over the winter months, telling the Dáil there were 12 outbreaks in nursing homes last week.
Mr Varadkar agreed that there is no certainty over what the country is facing this winter.
The Tánaiste told Mr Kelly that the health system and healthcare workers will be under a lot of pressure this year, due to the pandemic, but also other due to other illnesses and a backlog of patients.
He said additional resources have been allocated to health, referring to the €22 billion being spent this year and additional beds and ICU capacity.
He told Deputy Kelly that NPHET is considering the matter of serial testing in nursing homes and the extension of antigen testing to schools.
Booster vaccines for over-60s 'later this week'
The Minister for Health has confirmed that the administration of booster vaccinations for those aged over 60 will begin later this week.
"For those aged 60 to 80, that programme will start towards the end of this week," he said.
Mr Donnelly said "those aged 60 to 69 will go to the vaccination centres and those 70 to 79 will be vaccinated at their GPs".
He said those eligible for a booster vaccine will be contacted, which include people who are immunocompromised, healthcare workers and those aged 60 and above.
Asked if there are any plans to extend booster to the general population aged under 60, the minister said "right now, the additional group that NIAC is looking at is those with underlying conditions".
Half Moderna dose to be offered to health staff
Health staff who are offered a booster mRNA vaccine will receive a full dose of the Pfizer vaccine, or half a dose of the Moderna vaccine.
The authorised European Medicines Agency booster dose for Moderna is half a dose.
In his advice to the Minister for Health, Chief Medical Officer Dr Tony Holohan said multiple studies have shown that a mix-and-match strategy appears safe and effective in providing a significant immune boost and "may be most beneficial in those who initially received a non-mRNA vaccine".
However, the CMO noted that the EMA decision related to homologous boosting only - using the same vaccine as in the primary dose schedule.
Dr Holohan said that it was his understanding that a comprehensive account of the evidence underpinning the recommendation from NIAC will follow later this week.
He said that while health care workers are not themselves at increased risk of serious disease, NIAC has provided a dual rationale for the booster recommendation.
It will likely decrease the incidence in health care staff and decrease the likelihood of onward transmission to clinically vulnerable patients.
The Chair of the Irish Medical Organisation's GP Committee said he is relieved that NIAC has approved the roll out of booster vaccines to healthcare workers.
Dr Denis McCauley said he expects that all healthcare workers - in both public and private sectors - will receive the vaccine top up.
He said the booster shot will not completely prevent people from contracting the virus, but said it will definitely boost immune systems and having it is a "very sensible, basic step".
Additional reporting: Fergal Bowers, Fergal O'Brien, Tommy Meskill
