Australians aged 30 and over are now eligible to receive a fourth COVID-19 vaccine dose from next week following advice from the Australian Technical Advisory Group on Immunisation (ATAGI).

From July 11 ATAGI has recommended that people aged 50 to 64 years old should receive a fourth dose, while people aged 30 to 49 years old may choose to have a fourth dose.

People aged 65 and over are already eligible for a fourth dose.

Here's everything we know about the latest changes to Australia's COVID-19 vaccine rollout.

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Who is eligible for a fourth COVID-19 vaccine dose?

Everybody who is aged 30 and above will be eligible for a fourth dose of a COVID-19 vaccine.

This eligibility will start next week, on July 11.

Currently, only four groups of people are eligible for a fourth dose, including people aged 65 and over, First Nations Australians aged 50 and over, residents in aged care and disability settings and people who are immunocompromised.

Can I get a flu vaccine and COVID-19 booster at the same time?

In updated health advice, ATAGI said it is okay for patients to get both a flu shot and a COVID-19 booster on the same day.

"All COVID-19 vaccines can be co-administered (given on the same day) with an influenza vaccine," it said.

The group explained a resurgence of influence is expected in 2022 with borders reopening.

"If a person had a 2021 influenza vaccine in late 2021 or early 2022, they are still recommended to receive a 2022 formulation of influenza vaccine when it becomes available," it said.

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When should I get the fourth COVID-19 booster?

ATAGI recommends that eligible people only receive a fourth COVID-19 booster at least three months after they receive their third booster.

This has been reduced from four months.

What if I've recently had COVID?

Similarly, ATAGI recommends that eligible people wait three months after being infected with COVID-19 before receiving a fourth dose.

Health Minister Mark Butler said the new subvariants meant that many people who have previously been infected with COVID-19 are not automatically provided with protection.

"What is particularly unique and different around BA.4 and BA.5 (is) they're very good at evading people's immunity," he said.

"If you have immunity from vaccines or from having COVID, you're still susceptible. Just because you had COVID earlier in the year doesn't mean you're not at risk of getting it again with this third wave."

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Does it matter what brand of COVID-19 booster I receive for my fourth dose?

No.

Why can't people aged under 30 get a fourth dose?

The experts are not yet convinced of the science for younger people.

"ATAGI did not support making the fourth dose available to healthy adults under the age of 30 years as it was not clear whether the benefits outweighed the risks in this population group," the group said.

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What's the point of getting a fourth COVID-19 booster?

You're at a decreased likelihood of being hospitalised if you catch COVID-19.

According to ATAGI, "increasing the uptake of fourth doses in the most at-risk population groups during this time is anticipated to play a limited, but important, role in reducing the risk to individuals of severe outcomes while taking pressure off Australia's health care system".

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A second NASA rocket has been launched into space from Arnhem Land in the Northern Territory.

Video shows the spectacular launch, which took place last night after being delayed by two days due to strong winds.

It follows the first NASA rocket launch on June 26 from the Arnhem Space Centre on the Dhupuma Plateau, near Nhulunbuy.

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The space centre is privately owned and operated by Equatorial Launch Australia (ELA).

Equatorial Launch Australia executive chairman Michael Jones said the successful launch was a very exciting follow up to last month's launch. 

 "We were delighted to achieve another successful launch which further strengthens the capabilities of our team and of the Arnhem Space Centre," said Mr Jones. 

 A third NASA launch is scheduled to take place on July 12.

"We look forward to our third launch on 12 July and then onwards to the future of the Arnhem Space Centre and the Australian space industry."

Last month's launch was the first time since 1995 that a rocket took off from Australian soil and the first time for NASA launching a rocket from a commercial facility.

About 75 personnel from NASA are staying in Australia for the sub-orbital sounding rocket launches, which are on a mission to investigate heliophysics, astrophysics and planetary science phenomena only observable from the southern hemisphere.  

By his father's final act of heroism, Aiden McCarthy survived Monday's carnage at a July Fourth parade in suburban Chicago.

But the 2-year-old now is left to grow up without either of his parents – an orphan of America's bane of mass shootings.

Kevin McCarthy, 37, and his wife, Irina, 35, were among seven people who died following an explosion of bullets Monday from a rooftop into a holiday crowd in Highland Park, Illinois, the Lake County Coroner's Office has said. Nearly 40 others were injured.

Aiden was protected from the gunfire by Kevin's body, even as the man lay wounded, Irina's father and Aiden's grandfather, Michael Levberg, told the Chicago Sun-Times.

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Aiden "was pulled out from underneath his father, who was still bleeding, by good Samaritans," US Sen. Tammy Duckworth, an Illinois Democrat, told CNN's John Berman on Wednesday.

"Then, they went to work on his dad because his dad's leg was still bleeding."

The McCarthys had been looking forward to seeing the parade with their toddler, Levberg told the Sun-Times.

"They were crazy about their child," he said. "They were planning two."

After the gunfire subsided, Aiden – a little boy, all alone – "was walking in the street," his grandfather told the Sun-Times. It's an image others captured and shared on social media.

A neighbour, Adrienne Rosenblatt, saw Aiden's photo on a neighborhood watch page and began trying to connect him with his grandparents, she told CNN affiliate WLS.

Meantime, strangers caught in the chaos cared for the toddler, according to a verified GoFundMe campaign that his mother's cousin, Irina Colon, started after the shooting.

Dana and Greg Ring spotted Aiden after the barrage of shots upended the parade they'd come to watch, he told WLS. The pair tried to get him to police.

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"When we pulled in, the cops looked like they were getting ready for war," Greg said. "I'll never forget. I pulled up, and I said, 'This is not our kid. It's not his blood; he's OK. What should we do?'

"And the cop said, 'We can't be babysitters now. Can you take care of him?'

"We said, 'Of course.'"

Aiden did end up at a police station, where he was reunited with Levberg, the grandfather told Chicago Tribune.

"When I picked him up, he said, 'Are Mommy and Daddy coming soon?'" Levberg said Tuesday. "He doesn't understand."

"At two years old, Aiden is left in the unthinkable position; to grow up without his parents," the fundraising campaign said.

"Aiden will be cared for by his loving family and he will have a long road ahead to heal, find stability, and ultimately navigate life as an orphan," it said.

"He is surrounded by a community of friends and extended family that will embrace him with love, and any means available to ensure he has everything he needs as he grows."

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About A$3 million had been raised by Wednesday morning, according to the GoFundMe account, which will support the boy "and the caregivers who will be tasked with raising, caring for, and supporting Aiden as he and his support system embark on this unexpected journey."

For now, confronting an anguished reality may be the first step.

"I don't know how they're going to tell him," Rosenblatt said to WLS. How do you tell a "boy that Mommy and Daddy are in heaven now?"

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