Ireland is to administer some 84,000 Covid-19 vaccines next week, falling short of its weekly target because of ongoing supply issues.
The health service has struggled to ramp up its rollout of the vaccine after manufacturer AstraZeneca said there will be a shortfall of 75,000 doses of the vaccine over two weeks.
The company told HSE bosses that supplies will be made up by the end of the month.
The Government said that 100,000 vaccines would be delivered each week but those figures have been revised downwards to around 82,000 weekly.
HSE Chief Clinical Officer Colm Henry said that the vast majority of over 85-year-olds will be vaccinated by Sunday.
He said between 600 and 800 will be completed next week.
Mr Henry told RTÉ News At One that some GPs had experienced supply issues, but that 1,300 practices received the expected supply.
"One of the features of this programme is that we are completely reliant on supplies," Mr Henry said.
"We got a fairly short notice from AstraZeneca of a shortfall of supplies of the order of 75,000 over a two-week interval, but that will be made up, we are told, by the end of quarter one which is the end of March.
He said that 84,000 vaccines would be delivered next week and some 37,000 over-70s will receive their first dose of the vaccine.
Around 10,000 people with underlying conditions will also receive their first dose.
The Cohort 4 group includes people aged 16-69 with a medical condition that puts them at very high risk of severe disease and death.
Hospitals will be working to identify the 84,000 people who will be included in the revised vaccine priority list.