The interest isn't counted as earnings, but you will be assessed on the savings themselves.
For Disability Allowance, the first 50,000 of savings is disregarded, the next 10,000 is assessed at €1 per 1000, the next 10,000 is assessed at €2 per 1000 and anything over 70,000 is assessed at €4 per 1000.
Your savings will also be assessed in relation to your medical card - I don't have the exact figures to hand, but will post when I can get it.