The Health Service Executive and the Department of Health are being urged to widen the range of healthcare professionals eligible to administer the Covid-19 vaccine.
Radiographers, radiation therapists, retried medics and doctors looking to volunteer for free all claim they are willing to become vaccinators - but that their offers to help have been rebuffed.
Pharmacists also claim they are unlikely to work in mass vaccination centres in a row over fees.
The HSE recruitment drive for vaccinators is focused on doctors, nurses, paramedics, pharmacists, physiotherapists, midwives, and emergency medical technicians.
However, on Thursday, the HSE extended the closing date for vaccinator applications for a second time to 23 March. The closing date had initially been fixed for 2 March.
In the UK, the NHS is recruiting everyone it possibly can to vaccinate - including healthcare assistants, nursing students and non-medical professionals, as long as they have completed some form of life support or first aid training.
The HSE has said vaccinators will work 12-hour shifts in 37 mass vaccination centres across Ireland - and that it has received 2,500 applications to date to work in these centres.
However, the representative body for radiographers and radiation therapists has warned of a potential shortage of vaccinators when vaccine supplies eventually increase - unless a greater variety of medical professionals can administer the jab.
The Irish Institute of Radiography and Radiation Therapy has also contacted the Minister for Health to say its members could help free up doctors and nurses for non-Covid related frontline healthcare.
"We wrote to the Minister of Health in early January expressing our willingness to engage and get involved. We believe radiographers and radiation therapists are well placed to do this.
"We are highly trained skilled and trained professions. Many of us are involved in intravenous and inter-muscular injections as it is", explained the Institute's President Dean Harper.
"A lot of us are primed to go. There's been a huge expression of interest from our professional groups in getting involved in whatever way they can. We can't be constantly relying on doctors and nurses.
"They're being pulled and redeployed from other areas. It's causing other areas of the health service to effectively grind to a halt - or to build up waiting lists", he told RTÉ's Today with Claire Byrne.
"It's going to be a disaster ready to happen. We need as many people as we can. The more people can get involved ; the more hands on, the quicker we can get this rolled out", he said.
Retired medics over 70 also believe they should be allowed administer the vaccine.
'I think it would be reasonable for anyone in my position to take the relatively small risk involved in giving some service to the vaccination programme' said Dr Paul Moriarty, the former medical director of the Eye and Ear Hospital in Dublin - who is over 70 - but fully vaccinated.
'I feel we should be able to use our expertise and patient and people skills to help with this relatively mundane task- but it frees frontline staff to look after all the other things that needs to be done in the health service.
"It would be much better if people like me could step in to vaccinate and allow people go back to providing care for all the other diseases bar Covid', he said also on the same programme.
"Recruitment are only looking for people to work full-time but there's a huge cohort of doctors and nurses looking to volunteer; they aren't being looked at either. It would be really unreasonable not to reconsider this", he said.
The Irish Pharmaceutical Union is also warning that its members will not work in mass vaccination centres in a row over fees. The union says regulations signed by Health Minister Stephen Donnelly earlier this year mean pharmacists are entitled to €70 an hour for working as vaccinators in centres.
However, recent communications from the HSE and its recruitment agency CPL indicate pharmacists will be paid no more than €24.82 an hour - around a third of what they claim was agreed.
"The HSE's recruitment isn't honouring the rate of pay that has been approved by Government and is set down in statute. Pharmacists are not in a position to take roles in mass vaccination centres as a result.
"We've sought assurances and explanations, but it could be the case that the mass vaccination centres won't have any pharmacists working in them', said General Secretary of the Irish Pharmaceutical Union Darragh O'Loughlin.
In a statement, the Department of Health says the HSE is building its workforce for vaccine rollout but it is not intended that professionals such as phlebotomists or radiographers will be called upon
The HSE says it is working with a range of groups to ensure the maximum number of vaccinators.
When asked about those wishing to volunteer and disciplines excluded from becoming vaccinators, the HSE said it "is obliged to implement Government Policy in this regard and can only recruit those disciplines listed in the current relevant Statutory Instruments (SI698 of 2020 and SI81 of 2021).
"Should there be a new SI allowing other disciplines to be vaccinators, the HSE will be able to recruit from those disciplines" it explained.
The HSE says pay for those working in vaccination centres has also been sanctioned by the Department of Health and its main priority is to have a workforce specifically employed for vaccinations so rosters can be properly forecast.