A nurse gave a baby boy the wrong vaccine and then tried to cover up her mistake which meant the family couldn't be aware of possible harmful reactions.

Today, the nurse has been censured for the error after an investigation by the country's health watchdog, the Health and Disability Commission (HDC).

The decision comes two years after the mistake in July 2019.

Instead of the rotavirus vaccine, the nurse administered the baby with Prevenar 13, used to protect babies against pneumococcal disease, which the baby had already been given.

Essentially, the baby boy was given the same vaccination twice on the same day and missed out on the rotavirus jab, the HDC decision report said.

The next day the nurse was alerted to the error and instead of reporting it she made a second home visit to amend the records in the baby's Well Child book. She didn't tell the family about the mistake, the report said.

It is not clear in the report if the baby suffered any harm as a result of the error.

Deputy Health and Disability Commissioner Rose Wall criticised the nurse saying by attempting to cover up her mistake she failed to comply with her ethical and professional obligations.

"The nurse should have alerted the baby's family to her mistake, and her failure to report it led to a delay in the error being rectified," Wall said.

The baby's family weren't alerted to signs of possible reaction to the drug error in the baby, the commissioner said.

"Instead of owning up to her mistake, the nurse went to significant efforts in an attempt to cover up her error."

The nurse was referred to the Director of Proceedings and Nursing Council of New Zealand to consider whether a review of her competence and any further action is warranted.

The Deputy Commissioner also ordered the nurse to undertake further training on safe administrations of medications and to apologise to the family.

The family also won an apology from the nurse.