More than 250 children and adults in Shetland are to be revaccinated after it emerged vaccines at Lerwick Health Centre had been stored at an incorrect temperature.
Some affected vaccines include treatments for tetanus, polio, hepatitis B and whooping cough.
A total of 171 children and teenagers, as well as 91 adults, will be offered repeat vaccinations
NHS Shetland said it was "very sorry" and the cause was being investigated.
The health board said there would be no harm to patients from vaccines stored at the wrong temperature, but their long-term effectiveness may be reduced.
The flu vaccine has not been affected.
Minimise repeat risk
Simon Bokor-Ingram, director of community health and social care, said: "I am very sorry that this situation has arisen, and particularly for affected patients and parents.
"Whilst we have systems in place to prevent such events it is clear that on this occasion these did not work as intended.
"We are thoroughly investigating this so that we can minimise the risk of this happening again.
"Our priority is to move quickly to offer revaccination to those affected, and I am grateful to our staff who have reacted with speed to this situation, with our first revaccination clinic happening on Saturday 24 March."