Two busy nurses have been found to have breached patient rights by giving the wrong vaccine to a 15-month-old boy last year.
The child was not harmed but the deputy Health and Disability Commissioner, Meenal Duggal, said they and their employer should have done better.
The incident happened in mid-July last year at an unnamed medical centre.
Under the National Immunisation Schedule, the boy should have received the MMR II vaccine against measles, mump and rubella; Prevenar 13 against pneumococcal disease; and the Act-HIB booster against the haemophilus influenzae type B bacteria, which is a cause of meningitis.
He got the first two items correctly, but instead of the Act-HIB booster he received a vaccine meant to be given at age four against diptheria, tetanus, pertussis and polio.
Ms Duggal said one nurse, RN B, mistakenly chose the latter vaccine, Infanrix-IPV, to be given instead of the Act-HIB. She asked another nurse, RN C, to double check and this nurse failed to see the mistake.
Ms Duggal said RN B, who was busy, selected the vaccines ahead of time and placed them in a dish, to be given later. She would have put them in a dish, to be checked against a card spelling out the vaccines to be given at 15-months according to the schedule, but there were no cards available.
RN C, who was providing education on asthma inhalers to a patient in another room, agreed to check the vaccines but did not notice the error.
She said RN B had not told her the boy's age. She said she "checked the vaccines and the expiry dates, I recognised all of the vaccines as being childhood vaccinations so none of them stood out to me as not belonging, this is where the immunisation cards would have come in very helpful".
She also said, "I was in no position to be a second checker and should never have accepted that responsibility in that instance."
For her part, RN B realised the error straightaway and told the boy's mother after checking with a regional immunisation coordinator, who said the Infantrix-IPV vaccine "would not be harmful".
The parents had the child checked at a hospital emergency department that evening, and he was sent home with paracetamol.
Ms Duggal said RN C had a responsibility to ascertain the age of the child and check that RN B had selected the right medicines.
She told both nurses to apologise to the parents, adding the medical centre had a responsibility to ensure the immunisation cards were available to its staff.
Overall she did not believe the medical centre took all the steps that were reasonably practicable to prevent the nurses' errors.
The director of research at the Auckland University Immunisation Advisory Centre told RNZ there was no safety problem involved, simply a case of the 15-month-old boy needing to have the one he missed later.
Helen Petousis-Harris said what he received incorrectly was virtually identical to a vaccine he had received between the ages of six weeks and five months.
"If he'd been in another country with a slightly different [immunisation] schedule to New Zealand, he could well have received that vaccine or something very similar anyway. So he's actually not received something outside what a lot of countries would do normally anyway," Dr Petousis-Harris said.