A group of Australian scientists has called on the government to review its Covid-19 immunisation strategy over concerns that the Oxford/AstraZeneca vaccine was not effective enough to generate herd immunity.

Several immunologists and the opposition Labor party said on Wednesday Canberra should seek additional supplies of the BioNTech/Pfizer and Moderna vaccines, which trials show have higher efficacy — a measure of prevention of infection or severe disease — than the Oxford/AstraZeneca jab.

Some health experts are also advocating for a “pause” in the rollout of the Oxford/AstraZeneca vaccine next month. The proposal has been rejected by Canberra.

“Until we get more data that shows that AstraZeneca is as good as the others, the scientific and medical risk that you take is that you won’t get herd immunity,” said Andrew Miller, president of the Australian Medical Association in Western Australia. “The political risk is that you will get a good vaccine for the rich and a not so good vaccine for the poor”

Dr Miller said Canberra should halt the planned rollout of the Oxford/AstraZeneca jab and source vaccines with the highest efficacy. Because Australia has largely reined in the virus — unlike the UK or US — it should wait and source the best vaccines available to build public confidence, he added.

However, the government said the Oxford/AstraZeneca vaccine would provide vital protection against the virus and there were no plans for a policy U-turn.

“The AstraZeneca vaccine is effective, it is safe, and it’s a high-quality vaccine,” said Paul Kelly, Australia’s chief medical officer.

“It will be available as soon as the TGA gives its tick, which we expect will be in February,” he added, referring to the Therapeutic Goods Administration, the country’s regulator.

Australia’s vaccine strategy suffered a blow last month when a homegrown candidate developed by the University of Queensland and CSL was abandoned after several trial participants returned false positives for HIV. However, Canberra had a contingency plan and agreed A$3.3bn (US$2.6bn) of deals with pharmaceutical companies for alternative vaccines.

Its largest order is with AstraZeneca. The Anglo-Swedish drugmaker has agreed to supply 53m doses of its vaccine, which achieved an average efficacy of 70 per cent in trials. It has also ordered 10m doses of the BioNTech/Pfizer vaccine, which has achieved efficacy of more than 90 per cent and is also expected to be approved by the TGA next month.

Canberra has also agreed to purchase 51m doses of the Novavax vaccine, although these are not expected to be available until mid-2021.

Some scientists are concerned by Australia’s reliance on the Oxford/AstraZeneca vaccine, noting that trial data showed that when the jab was given as two full doses at least a month apart, its efficacy was only 62 per cent.

“Pivoting towards the Moderna and Pfizer vaccines looks like a good idea in an ideal situation,” said Stephen Turner, president of the Australian and New Zealand Society for Immunology.

He called a review of Canberra’s vaccine strategy appropriate but warned there were practical difficulties in rolling out the BioNTech/Pfizer vaccine because it needs to be stored at minus 70C. The Oxford/AstraZeneca vaccine, which can be kept at 2C to 8C, could be a useful tool in the short term to control the virus, said Mr Turner.

The Australasian Virology Society said it did not support a “pause” in vaccine rollout. Rather, all the data should be analysed for safety and efficacy by Australia’s medicines regulator before a final decision to roll out the Oxford/AstraZeneca vaccine, it said.

The Labor party said the government should agree more deals with vaccine manufacturers, noting it had three contracts while other developed economies had five or six. But it has not called for a pause in the rollout of the Oxford/AstraZeneca vaccine.

Peter Collignon, professor of microbiology at Australian National University, described calls to halt the rollout as “unrealistic”. He said it was unlikely the government could source enough alternative vaccines this year and it was crucial to get high-risk people vaccinated before winter.