More charges are expected to be laid against a nurse in Samoa in relation to the deaths of two toddlers who died shortly after receiving MMR vaccinations.

Local authorities investigating the deaths of 1-year-olds Lannacallystah Samuelu and Lameko Si'u last night announced that one of the nurses involved had been charged by police over the weekend.

The children died last month at Safotu District Hospital, in Savaii, within minutes of getting a measles, mumps and rubella shot.

The female nurse was brought in by authorities and officially charged on Saturday.

The exact charge has not been released by the Attorney General Lemalu Herman Retzlaff - who is assisting in the investigation - but Samoan media quoted informed sources who said the charge was of conspiracy to defeat the course of justice.

The woman will appear in court on August 14.

News from Tala fou o Samoa said more charges are expected to be confirmed publicly, as well as the one she has already been charged with, then.

Retzlaff said a file was given to his office last week.

After more investigations involving Samoa Police's criminal investigation department - both in Savaii, where the deaths occurred, and the main island of Upolu - a decision was made to charge one of the nurses.

"The decision to charge was thereafter supported by advice and it is also confirmed by police that investigations are still active and ongoing,'' he said.

The deaths prompted Samoa's Ministry of Health to stop all MMR vaccinations on the island nation until the completion of the investigation. Every unused and partly used vaccine was recalled.

A coronial inquest into the deaths has been adjourned for a second time; after the prosecution said this week they were yet to receive the children's postmortem examination results.

The inquest has been adjourned to September 12.

Since the deaths, doctors and health experts have been quick to reassure members of the public - particularly the Pacific and Samoan communities - that the vaccine itself is very safe.

In this tragic case, vaccinologists say they believe the problem was not in the vaccine itself, but how it was prepared before it was administered.

A spokeswoman for the Auckland Regional Public Health Service told the Heraldinformation from the three local district health boards - Auckland, Waitematā and Counties Manukau - indicated there had been no impact on the rates of MMR immunisation.

"Everyone is keeping an eye on it,'' she said.