World health authorities are now helping Samoan officials investigating the deaths of two children who died shortly after receiving an MMR vaccination.
The World Health Organisation and the United Nations International Children's Emergency Fund (Unicef) have issued a statement indicating their involvement in the tragic case.
"Unicef and the WHO are deeply concerned about the deaths of two children in Samoa last week after they received a routine measles, mumps and rubella (MMR) vaccine.
"The deaths of these two children is a tragedy and our thoughts and prayers are with their families and the people of Samoa.''
A spokesman for the organisation said representatives were working closely with the Samoan Government; whose Prime Minister this week called for a full inquiry into the circumstances of the deaths of the two 1-year-olds who died after receiving a vaccination at Safotu District Hospital, on the island of Savaii, last Friday.
The autopsies of youngsters Lannacallystah Samuelu and Lameko Si'u - the latter celebrating his first birthday a few days ago - are due to take place this week.
It is understood both Unicef and WHO representatives are due to touch down in the island nation today.
"A Government-led investigation, including autopsies, is underway and until it is complete we will not know the cause of this tragedy,'' the spokesman said.
The Samoan public was officially told of the deaths on Monday; after its Ministry of Health announced that all MMR vaccinations would be halted and all vaccines - partly used and unused - were being recalled, nationwide.
News of the deaths became widely known in the island nation earlier, however, after distraught family members revealed the situation and posted photos of the dead children on Facebook over the weekend.
Fears after deaths:
Members of the Pacific Island community have started to question the safety of the vaccination and discussing whether or not they should be taking their children to get the recommended shots.
Those in the Samoan community, both abroad and in New Zealand, have debated the safety of vaccinations via social media platforms and on radio talk-back on Auckland-based radio station Radio Samoa.
However, experts have stressed that the case of the deaths in Samoa is very rare and that, in fact, the vaccine is very safe.
University of Auckland vaccinologist Dr Helen Petoussis-Harris said yesterday that there had not been a death associated with the MMR vaccine in New Zealand over the many decades it had been administered here.
She said there were two reasons that could have resulted in the children's deaths in Samoa.
"One is that there's been an error where the vaccine is prepared for the injection incorrectly and ultimately results in the wrong substance being injected,'' she said.
"Or there's been some sort of contamination due to the vaccine having been reconstituted and left at a room temperature for a really long period of time.''
Meanwhile, a police investigation is also underway after the families of the two children made formal complaints with authorities in Samoa.
The two nurses involved have been stood down for their own safety, Samoan authorities said, as the investigation continues.