The tragic death of two babies after receiving the mumps, measles and rubella (MMR) vaccine in Samoa last Friday continues to be under investigation.
Both a one-year-old girl and one-year-old boy died within minutes of being injected by nurses at Safotu Hospital in Savaii.
The deaths occurred within two hours of each other.
"We now have a full scaled inquiry as ordered by the prime minister so the prosecution has taken over," says Ministry of Health chief executive Dr Take Naseri.
"They are going to work hand in hand with our forensic pathologists."
He says the vaccines were obtained from UNICEF and there was a need to discuss "the procurement and quality" of them.
"We are looking at labs that can actually test the vaccines, there’s one lab in Australia," Dr Naseri told 1 NEWS.
"There’s also an immunisation expert down from our main office in the West Pacific region who has done previous investigations on vaccinations."
The two nurses who administered the vaccinations have since been removed from the "tense atmosphere" for their own safety.
"We are providing counselling, we advise them to go on light duty basis."
"We don’t want them to think this is a penalty for them," Dr Naseri says.
The MMR vaccine is recommended for all children in New Zealand, and the Ministry of Health says it has an “excellent safety record”.