A 14-year-old girl died two days after being discharged from a hospital following "serious failings", an inquest heard.
Josie Cotier died at her Clacton home from bronchopneumonia in the early hours of 22 October last year.
Doctors at Colchester General Hospital had missed a "red flag" in their sepsis protocol, Essex Coroner's Court heard.
The hospital apologised to the family and said work had been done to ensure such incidents would not happen again.
Josie, who had learning difficulties, was admitted to the hospital on 20 October suffering from diarrhoea and vomiting but was discharged later the same day, the inquest was told.
The next day she suffered cold sweats at 21:00 BST and her parents rang the hospital, speaking to a junior doctor who did not raise concerns.
At 02:40 BST on 22 October she was found unresponsive by her parents who were unable to resuscitate her.
The inquest heard a lack of communication between nursing staff and doctors had meant warnings had been ignored and test results had not been followed up.
Dr Andrea Turner, who was the clinical lead for children's services at the time of the incident, told the inquest an extensive investigation had taken place and the trust's policies had been changed to ensure there would be no repeat of the death.
She said: "In the warning protocol there was a red flag for sepsis and two amber flags which were not taken into account and examined further.
"If they had been checked she would definitely have been admitted."
She added: "If she had been admitted it is quite possible she would not have died."
In her conclusion, coroner Caroline Beasley-Murray said: "There were serious failings in the care provided. If appropriate care had been provided she might have survived."