NINE-year-old Jesse Newman died of heart failure thirteen minutes before Father's Day last September.

He had been diagnosed with chickenpox three days earlier.

Today Jesse's mother Renay spoke about the experience that devastated her family as a timely warning in the lead up the chickenpox season, which begins in early spring and peaks in January.

Like most Australians, Renay Newman believed chickenpox was a relatively benign illness and a normal part of growing up.

Jesse came home from school the Monday before Father's Day with a headache.

He had a restless night, broken by bouts of vomiting, but Renay felt no need to panic.

Chickenpox was going around the school and many of the local children had come down with it.

By Wednesday, when the telltale blisters appeared, Mrs Newman took Jesse to the doctor, who confirmed chickenpox and sent Jesse home with a dose of antibiotics.

By Friday Jesse's condition had deteriorated and he was taken to the local hospital at Singleton. He developed trouble breathing and was transferred to Maitland Hospital.

It was then that Mrs Newman experienced her first misgivings.

"That's when I started to get very worried," she said.

"I didn't feel the need to be worried before that, he had no temperature and I had no warning."

Jesse was diagnosed with pneumonia at John Hunter Hospital and died just before midnight.

Chickenpox kills around four people each year, most of them children.

In the majority of cases chickenpox, a highly contagious disease transmitted by coughing or contact with the rash, comes and goes.

However, sometimes chickenpox can lead to pneumonia or swelling of the brain, known as chickenpox encephalitis, says Dr Jenny Royle, of the Royal Children's Hospital immunisation centre.

"Chickenpox as a disease has an enormous spectrum of clinical illness," she said.

"This can range from someone not knowing they have the illness ranging right through to quite devastating disease."

Chickenpox vaccines, not currently available on the childhood schedule, had been available in Australia for two years.

GPs can administer the vaccine, which costs about $50, to children over the age of 12 months.

Mrs Newman said the biggest tragedy was that her son's death was preventable.

"Chickenpox might sound trivial but it's not," she said.

"This is something preventable.

"Get your kids vaccinated ... the last thing you want to do is sit there and watch your child die."