He said the "worst-case scenario" would see Ireland only receive 10% of the expected 600,000 Johnson & Johnson vaccines.
Minister for Health Stephen Donnelly has said that there may be a "significant under-delivery" of Johnson & Johnson vaccines.
As a result, the Minister added that he is "unclear" whether it will be possible to meet the Government target of 80% of adults receiving one dose of a Covid-19 vaccine by the end of June.
Donnelly told the Dáil on Thursday morning that there are also "questions around" the delivery of the AstraZeneca vaccine to Ireland.
He said that he was "just off the phone to the task force", who cited "serious concerns over the supply of the Janssen vaccine".
Donnelly said that Ireland had a contract for 600,000 J&J vaccines for June, but that under delivery of the vaccine means that, in a best-case scenario, 235,000 vaccines will arrive and, in a worst-case scenario, 60,000 vaccines will be delivered.
"In short, it looks like we're going to get a significant under-delivery on Jansen, and there are question marks over what is going to come in from AstraZeneca," he said.
Donnelly added that Ireland had opted in to an EU purchase agreement which will see 1.8 billion Pfizer/BioNTech vaccines delivered into Europe, which he described as a "significant advancement".
He also said that while vaccinations have been able to continue "uninterrupted", the cyber attack on the HSE has "had an impact".
The Minister noted that half the adult population will have received at least one Covid-19 vaccine dose by the end of this week, as at least 280,000 doses will be administered following a record delivery of 300,000 jabs last week.
"We believe that by the end of this week, half the adult population in our country will have received at least one vaccine dose," he said.
