The Samoan Government has seized the MMR (Measles, Mumps and Rubella) vaccine from around the country and launched an investigation following the deaths of two babies last Friday.
The first baby, a 1-year-old girl, died within three minutes of being injected by the vaccine by a nurse at Safotu Hospital in Savaii.
Two hours later, another family brought their baby, a 1-year-old boy, to the hospital for his vaccination.
According to TV1 Samoa, when the family heard about the first death they refused to let their son be vaccinated but allegedly the nurse did it without the parents' consent.
He died within a minute of being injected.
The Ministry of Health CEO Dr Take Naseri has ordered the immediate withdrawal of the vaccine and all hospital staff involved have been stood down.
Prime Minister Tuilaepa Sailele Malielegaoi has sent his condolences to the families and says he has called for a full inquiry into this "devastating incident".
"There are already processes that will determine if negligence is a factor - and if so, rest assured, those processes will be implemented to the letter to ensure that such a tragedy will not be repeated and those responsible will be made to answer," he said.
Note: The MMR vaccine is recommended for all children in New Zealand, and the Ministry of Health says it has an "excellent safety record".