Australia's chief medical officer has rejected calls to pause the rollout of the AstraZeneca vaccine, insisting it is completely effective in preventing serious illness and death from coronavirus.
Some doctors are concerned about the vaccine's efficacy rate, which ranges from 62 per cent to 90 per cent, depending on how doses are administered.
The doctors fear this may not be enough to achieve herd immunity and protect enough of the Australian community from the virus.
They are calling on the government to reshape its vaccine strategy and pivot to alternative candidates such as the Pfizer and Moderna jabs.
But Chief Medical Officer Paul Kelly is standing by plans to distribute AstraZeneca to most Australians.
He has challenged the focus on efficacy rates published in a medical journal in December.
"In terms of preventing death, it works 100 per cent of the time. In terms of preventing severe illness, it works 100 per cent of the time," Professor Kelly told Sky News on Wednesday.
He said AstraZeneca's candidate exceeded the World Health Organisation's minimum efficacy rate for vaccinations.
The federal government has ordered 54 million doses of the AstraZeneca vaccine and plans to give it to most Australians, pending approval by the Therapeutic Goods Administration.
Professor Kelly is standing by the strategy, which has been in planning for many months, pointing out alternatives such as the Pfizer vaccine cannot be manufactured in Australia.
"The great advantage of the AstraZeneca vaccine is it is being made here in Australia. It will be available as soon as the TGA gives its tick, which we expect that it will in February," he told the ABC.
Australia has supply agreements in place for the AstraZeneca, Pfizer and Novavax vaccines.
There is a deal for 10 million Pfizer doses to vaccinate five million Australians, with the first doses to be given to frontline health and border workers.
The federal government has not struck a deal for Johnson and Johnson or Moderna, whose drug is easier to distribute than the Pfizer vaccine.
Johnson and Johnson has applied for a provisional designation with Australia's medicines regulator.
Professor Kelly expects the Novavax candidate or another protein vaccines to be the long-term option around the world.
"We have backed many horses. We have several eggs in the basket. We have, from the beginning, looked for a diversified portfolio of vaccines," Professor Kelly said.
Labor health spokesman Chris Bowen rejected calls to pause the AstraZeneca rollout but criticised the government for not having more options available.
"A pause only works if you've got something to replace it with," he told ABC radio.
WA Health Minister Roger Cook said he had spoken to a number of doctors who were concerned about the efficacy of the AstraZeneca vaccine.
"Obviously there's an emerging view and evidence that the Pfizer vaccine is the highest standard and is more effective," he told Perth radio 6PR.
"And that's why I think people are looking to that and asking the question about why we can't secure more for the Australian community."
Australian Associated Press