Parents of children who were vaccinated for MMR and Varicella at Essentia Health-Duluth have been advised to bring them back for a do-over.

In a statement, Essentia Health said parents were advised “out of an abundance of caution and concern” to bring their children in for an additional dose of the Varicella or Proquad vaccinations because the earlier dose “was not stored at the manufacturer’s recommended temperature.”

A spokeswoman for Essentia declined to say how many children were affected or over what period of time. No explanation was offered about how the mistake occurred.

“We have put measures in place so this does not occur again and apologize for any inconvenience,” the statement concluded.

MMR is a vaccination that covers measles, mumps and rubella. Varicella is also known as chickenpox.

The vaccinations are given by injection.