Healthcare staff will not be able to choose which Covid-19 vaccine they receive according to the Health Service Executive (HSE).
Trade unions were informed of the decision after they expressed members' concerns about receiving the "least efficacious vaccine", according to The Irish Times.
Following the decision of the National Immunisation Advisory Committee (NIAC) to offer only the Pfizer/BioNTech and Moderna vaccines to people over the age of 70 in the community, the AstraZeneca vaccine was instead earmarked for healthcare workers.
The NIAC's decision was based on a recommendation by the European Medicines Agency (EMA), noting there was a lack of evidence regarding the efficacy of the AstraZeneca shot among older people.
The unions also relayed staff concerns relating to the vaccine's efficacy among other age groups, reported to be approximately 60 per cent, compared to the 95 per cent and 94.5 per cent efficacy of the Pfizer and Moderna shots respectively.
Despite the unions' concerns, the HSE confirmed it would not be reviewing its decision.
"Administering the effective vaccine that we have available as quickly as possible to healthcare workers will offer substantial protection to the majority of healthcare workers who receive it within three weeks of the first dose," the HSE said.
In a letter to a staff panel earlier this week, the HSE's chief clinical officer Dr Colm Henry confirmed the HSE "is not in a position to offer healthcare workers a choice of vaccines at this time".
Dr Henry added recent studies have also suggested the AstraZeneca vaccine has a higher efficacy rate than previously indicated, with recent data reporting 70 per cent effectiveness and no cases of hospitalisation or severe Covid-19 from 21 days after the first dose of the vaccine.
He added there are also reports of the efficacy increasing to 82 per cent after the second dose is administered when there is a 12-week interval between doses, which is the schedule currently being used.
Dr Henry added it would be "irresponsible" of the HSE not to proceed with offering the available vaccine as quickly as possible.