Two senior Samoan nurses have each been sentenced to at least five years in jail after they incorrectly mixed and administered vaccinations that caused the death of two infant children.

Key points: The deaths were caused by human error and the vaccines were incorrectly mixed

The deaths were caused by human error and the vaccines were incorrectly mixed One mother described her daughter's body 'turning black' after the fatal injection

One mother described her daughter's body 'turning black' after the fatal injection Samoa is now trying to re-instil confidence in its health system

The decision was handed down after the nurses, Luse Emo Tauvale and Leutogi Te'o, pleaded guilty to manslaughter after giving the children a routine mumps, measles and rubella (MMR) vaccination in July last year.

Tauvale pleaded guilty to two charges of manslaughter and one charge of obstruction of justice.

She mixed the vaccine powder with an expired anaesthetic, the court was told, and was sentenced to five years and six months in jail.

Te'o pleaded guilty to one charge of manslaughter and was sentenced to five years in prison.

"You did not intend for this to happen, you [have been] a registered nurse for many years," acting chief justice of the Supreme Court, Vui Clarence Nelson, said in handing down Tauvale's sentence.

"I have no doubt the knowledge that your actions led to the death of two young children is something you will carry to your grave; as will the parents," he said, according to a report in the Samoa Observer.

The girl and boy were just 12 months old at the time of their deaths.

Mother Mareietta Tuisuesue told TV1 Samoa last year that she noticed her daughter ailing after she received the shot.

"Her body was turning black, so I ran back up to the doctor. She was still breathing at the time," she told TV1 Samoa.

"Not long after that, they came out and told me that my daughter had passed away."

Also speaking to TV1 Samoa at the time, mother Punipuao Si'u said she had asked for her son not to get vaccinated after she learned that the little girl had died following the same vaccination at the same hospital on the island of Savai'i two hours prior.

It is alleged the vaccination then went ahead without the mother's consent.

Ms Si'u described how her son's head dropped and his eyes closed just minutes after the fatal shot had been administered.

"I ran back into the hospital. I cried and watched as they worked on my son. I asked: 'How is my baby?'" she told the television station at the time.

"They didn't say anything to break it to me gently or calm my heart, they just said: 'He's finished'."

Both parents told TV1 Samoa that they accepted the court's decision and had already forgiven the two nurses.

Case shakes faith in Samoan health system

The emotionally charged case sparked fears in Pacific nation about the safety of vaccinations, with the Samoan Government issuing an immediate recall on the MMR vaccine.

But Samoa's Ministry of Health found last month that the deaths were caused not by the vaccines themselves but by human error.

Each vial of the MMR vaccine needed to be mixed with a vial of diluent, but the health ministry said the nurses mixed the vaccine with the wrong liquid.

Rasul Baghirov, the WHO's Samoa representative, told the ABC's Pacific Beat program that the case had shaken faith in Samoa's health system.

"People were basically living with little information and some rumours," he said.

"Parents are also scared to bring their children to vaccinate for other diseases."

Elizabeth Powell, the general manager of Pacific Health in South Auckland, said last month that eight nurses of Samoan heritage had been sent from New Zealand to the Pacific nation in an effort to restore confidence.

"When something like this happens, it does shake the confidence a little bit in the communities, around [the question of] is my child safe?" she told Pacific Beat.

"[We need] to help the people of Samoa to actually regain confidence and trust again in the health system."