Sue Grey, the anti-vaccination lawyer acting for the parents, told Radio New Zealand the surgery went ahead on Friday and the boy was doing well.

The baby has a congenital heart defect and needed life-saving surgery, which his parents were not willing to go ahead with if blood transfusions were used from people who been vaccinated for COVID-19.

New Zealand's health authority, Te Whatu Ora, went to court seeking temporary guardianship of the boy in order to authorise the use of vaccinated blood during the operation.

A judge at the High Court in Auckland placed the baby under temporary guardianship of the court earlier this week and ruled that doctors could make the medical decisions for the baby.

An additional court ruling, made the night before the surgery, ordered the parents not to prevent medical staff from carrying out their work after they stopped doctors from taking blood tests, performing a chest X-ray and an anaesthetic assessment, Radio New Zealand reported.

The boy's parents told the court they had other willing donors lined up who had not been vaccinated against COVID-19.

However, the boy was likely to need plasma products which are formed from pooling blood from various donors. Doctors argued it was "simply impractical" to get this from directed donors, news website Stuff reported.

About 60 protesters gathered near Starship Children's Hospital in Auckland on Friday morning, according to Radio New Zealand.

The protesters were pictured holding placards with anti-vaccination slogans.