A data leak earlier this year saw the personal data and even laboratory test results of some 6,000 patients posted online, said the National Institute for Health and Welfare (THL) on Tuesday.
The data ombudsman informed THL of the leak in August. The institute then removed the data from two online services where the data had been available to view.
THL attributed the leak to 'human error', and said that the data did not include home addresses or complete medical records. It did include names, personal ID numbers and information about a bacteria's resistance to antibiotics.
Those affected by the leak have been sent a letter in which THL apologised for the leak.