Australians with their first shot of AstraZeneca are being urged to follow up with their second dose – or they put themselves in the path of the dangerous Delta variant, infectious diseases experts have warned.

Their advice comes after the highly contagious COVID-19 variant was detected in New South Wales and possibly Queensland.

But it’s becoming increasingly hard to get the message of vaccine urgency through.

Public confidence in AstraZeneca plummeted again last week after the Morrison government recommended the jab now be limited to those older than 60.

The change in advice came a week after a second Australian, a 52-year-old woman, died following rare complications after receiving the AstraZeneca shot.

It was the latest stumbling block in a national vaccine rollout plagued by supply issues and mismanagement.

Now, government and health officials alike have been working desperately to persuade eligible Australians to get the AstraZeneca jab, and for those who have had their first dose to get their second.

• Read: NSW expands COVID restrictions as locally acquired cases grow

How AstraZeneca can help

The highly contagious Delta variant, first identified in India, is fast becoming the most dominant global strain.

That’s largely due to its extreme ability to spread during the most fleeting exposure, such as a quick chat with a barista at a cafe.

But it’s not all bad news.

Studies show the Pfizer and AstraZeneca vaccines are “highly effective” against symptomatic disease from the Delta variant – but only after two doses.

That’s why health experts are encouraging all Australians who have received one AstraZeneca dose to stay the course and get their second one.

“The risk of getting these rare blood-clotting side effects is incredibly low for the second dose,” said Professor Adrian Esterman, an epidemiologist at the University of South Australia.

• Read: ‘Near and present danger’: Delta strain makes fixing hotel quarantine job No.1

Ian Mackay, an associate professor at the University of Queensland’s school of medicine, agreed.

“The risk of TTS (thrombosis with thrombocytopenia syndrome) on the second dose is far reduced compared to the first dose, so if you’ve been fine with the first dose, you’ll be fine with the second,” he said.

Without a second dose, both the Pfizer and AstraZeneca vaccines are only about 30 per cent effective against the worrying Delta variant.

“That’s nowhere near good enough,” Professor Esterman told The New Daily. 

“It requires a minimum of 50 per cent for it to be useful.”

After two doses, researchers found the AstraZeneca jab was at least 60 per cent effective against Delta – but said there was data demonstrating it takes longer for the two doses to become fully effective.

Recent data from Public Health England shows two doses of the mRNA-based Pfizer vaccine can be 96 per cent effective at preventing hospitalisation or death caused by the Delta variant.

The trouble is, Pfizer vaccine is in short supply in Australia.

The Morrison government has said Australia will receive 40 million doses of the Pfizer jab this year, but it’s unclear how many doses are available right now.

National cabinet will meet on Monday to discuss what the increased reliance on Pfizer imports means for the national rollout.

In the meantime, the Victorian government announced on Sunday it would invest $5 million in facilitating mRNA vaccine production onshore.

The money will go to Monash Institute of Pharmaceutical Sciences, which is working on its own mRNA coronavirus vaccine candidate.

Phase 1 clinical trials are due to start in October, in collaboration with the Doherty Institute, with preliminary results expected to be made available in the first half of 2022.

If all goes well, having mRNA vaccine manufacturing capabilities in Victoria could potentially alleviate our reliance on Pfizer deliveries from overseas.