The highly infectious Brazilian COVID-19 variant threatens to undermine Australia’s vaccine rollout if it rips through the country before our program is complete, a top epidemiologist warns.

Deadly and fast-spreading, this strain also has the ability to reinfect recovered cases.

But as of Sunday night, Australia has not moved to halt international flights from Brazil.

Professor Marylouise McLaws, a UNSW epidemiology professor and adviser to the World Health Organisation, said the emerging threat was all the more reason to vaccinate all Australian quarantine workers as soon as possible.

“There should be no delay,” she told The New Daily. 

“The only way for this to sneak into the community is via quarantine.”

• Read: COVID vaccine: 500,000 inoculated, just 24.5 million to go

Home to less than 3 per cent of the world’s population, Brazil accounts for almost a third of the daily global deaths from COVID-19, driven by the new variant, known as P1.

More than 300,000 people have died, and daily deaths now total 3000 – a toll recorded only by the far more populous United States.

Brazil surpassed 100,000 new cases in one day on Thursday last week. Photo: Getty

Not only is the variant deadly, it’s resilient.

Earlier this month, a study found it can reinfect people who had recovered from the disease.

Out of 100 people in the Amazon jungle city of Manaus who had recovered from infection with COVID-19, somewhere between 25 and 61 of them are susceptible to reinfection with P1, said Dr Nuno Faria, a virus expert at Imperial College London who co-led the research (which has not yet been peer reviewed).

The scientists estimated P1 was 1.4 to 2.2 times more transmissible than the initial form of the virus.

It’s too early to say if the variant’s ability to evade immunity from previous infections means vaccines won’t work as well against it.

Either way, the strain has worried foreign governments.

In January, the UK introduced a ban on all international arrivals from South America over fears of the Brazilian strain.

The risk to Australia

Keeping the Brazilian strain out of Australia until our vaccine rollout is complete is crucial to keeping us safe, Professor McLaws said.

“When you start partially vaccinating a community and you have a particular variant of concern circulating, then that virus learns how to get around a partial immune response,” she said.

For example, if you’ve only had one jab of the AstraZeneca or Pfizer vaccine and then come into contact with the Brazilian strain, the virus can learn how to get around your partial immune response and mutate.

It’s not until you’ve got two shots of the vaccine that you’re fully vaccinated and protected from serious illness.

Until then, the virus can still infect you and get a head start on working around the vaccine.

“Like all viruses, the longer COVID circulates in a community, the greater the risk of it mutating,” Professor McLaws said.

“The viruses don’t mutate to kill you, as that’s not in their best interests. They mutate to become highly infectious.”

But she said the Brazilian strain was leaving many scientists scratching their heads.

“The last time we had a meeting at WHO, where vaccinologists shared what they knew about variants of concern, the jury was still out on the Brazilian one,” Professor McLaws said.

“There weren’t enough people vaccinated yet to say whether it does or does not cause an impact on the efficacy of vaccines.”