Hospitals in Ireland have been forced to cancel non-emergency operations because of a severe shortage of blood.
The restrictions involve residents of the UK in the 1980s and 1990s
Donations have fallen since controls were introduced last year on people who have lived in the UK from giving blood.
The restrictions were brought in over fears about variant CJD from the UK infecting Irish blood stocks.
The Irish Blood Transfusion Service (IBTS) is asking hospitals not to carry out elective surgery after seeing a 9% drop in donations.
In Ireland, about 6% of the population are blood donors, a figure broadly in line with the rest of Europe.
But new restrictions on who was allowed to give blood at clinics were introduced late last year, preventing many people who have lived in the UK from doing so.
The IBTS says 4,000 fewer people have attended clinics in recent months.
Anyone who lived in the UK for a year or more between 1980 and 1996 is now excluded from giving blood.
The BBC's Dublin correspondent James Helm says non-emergency operations have been cancelled for the next few days.
The health authorities hope the shortage will be eased by regular donors making an extra trip to the clinic to give blood.
Contaminated beef was the cause of most cases in the UK, but transfusion experts believe there is a potential for vCJD to be transmitted through blood or blood products.