A woman in the United States has died of coronavirus after she refused the vaccine because of concerns over side effects, her family have said.

Tricia Jones, 45, a mother of two from the US state of Missouri, died on June 9 after contracting the highly-infectious Delta strain.

Her mother Deborah Carmichael told local news station Fox 4 that Jones had been hesitant about getting the vaccine.

"She was afraid of the side effects, I think. You hear a lot of horror stories," Carmichael said.

"I, myself, when I had the shot, it was rough, so it scared her and freaked her out. So she didn't want to do it. I couldn't convince her."

Carmichael now hopes her daughter's death can serve as a warning to others hesitant about getting the vaccine.

Ms Jones' mother said her daughter had been scared to get the vaccine. (Photo / Fox 4)

Jones contracted the Delta variant of coronavirus in April alongside her husband after their son contracted the virus at school.

She was hospitalised and on May 13 was put on a ventilator but tragically died less than a month later.

"After she got it, she said, 'Mum you were right, about the shot, about masks, being diligent and all that'. I was like, 'I don't want to be right. I want you to be well. That's all that matters'," Carmichael said.

Jones leaves behind her husband and two children including her 18-year-old daughter Adriana Jones, who has autism.

Adriana said Jones had been her "best friend" who had helped her through being bullied at high school.

The mother and daughter had both been planning to study together at their local community college later this year.

Carmichael asked people to "please take this seriously" and get vaccinated.

"You don't want to see a family member you love go through this," she said. "You have a way better chance of coming out okay than if you don't."

As Sydney grapples with its growing outbreak of the Delta variant intensive care doctors are treating seven covid-19 patients, including a person aged in their 30s.

A further 30 people have been hospitalised with the coronavirus disease, and two of the ICU patients are on ventilators.

Eight of the hospitalised people are under the age of 35.

The Delta strain was first detected in India in October last year and has now spread to at least 62 countries.

In the UK it accounts for 99 per cent of all cases and is the highly infectious strain behind Sydney's latest outbreak.

The variant is twice as infectious and if contracted patients are more likely to end up in hospital.

Delta's symptoms are also more severe, with doctors reporting severe diarrhoea, hearing impairment and blood clots that lead to gangrene in cases with the variant.

"Last year, we thought we had learned about our new enemy, but it changed," Dr Abdul Ghafer, an infectious disease physician at Chennai's Apollo Hospital, told Bloomberg.

"This virus has become so, so unpredictable."

The Delta strain was responsible for India's staggering second coronavirus wave in April and May that led to its death toll doubling to 330,000.

- Hanna Paine, news.com.au