AstraZeneca vaccine: why Australia is forging ahead as South Africa tackles Covid variant

Medical experts say the jab is effective against severe infection, as researchers work to adapt vaccines against variants and experiment with mixing inoculations

Australian health authorities have moved to calm concerns about
the effectiveness of the AstraZeneca vaccine, after a small-scale study suggested its efficacy against mild to moderate infections from the the South African variant of the virus could be as low as 10%.

AstraZeneca is going through the Therapeutic Goods Administration approval process now and is slated to be rolled out from April. This is what experts are saying.

You should still get the AstraZeneca vaccine

That’s the advice of Australia’s chief medical officer, Prof Paul Kelly. He has urged people not to put too much stock in the results of the South African study, which he stressed was both limited in scope and had not yet been peer-reviewed.

Kelly told reporters on Tuesday that people should be wary of “taking small amounts of information quickly, without looking at it carefully, and making conclusions”.

“At the moment, I can absolutely say – and this may change in future, and we will be nimble in the way we look at that information and putting that into our planning – but at the moment, there’s no evidence anywhere in the world that AstraZeneca effectiveness against severe infection is affected by any of these variants of concern. And that is the fact.”

His comments were echoed by Prof Mary-Louise McLaws, an Australian epidemiologist and advisor to the World Health Organisation on Covid-19.

“I commend your readers to get any vaccine that is offered to them, because it will reduce severity,” McLaws told Guardian Australia. “Any vaccine is better than no vaccine. If you do get the virus it will improve your outcomes, your response, and you may not get severe Covid.”

There is also evidence from another unpublished study in Israel on the Pfizer vaccine, which suggested that people who are not protected by the vaccine nevertheless had a reduced viral load. So even if a vaccine had a reduced efficacy, there is evidence to suggest it will reduce the extent to which a person spreads the disease, McLaws said.

AstraZeneca, unsurprisingly, also played down the study on the South African variant, saying it was a small phase one or two trial, which showed limited efficacy against mild disease from the variant.

“While we have not been able to properly ascertain its effect against severe disease and hospitalisation given that subjects were predominantly young, healthy adults, we do believe our vaccine will still protect against severe disease for the B1351 variant, particularly when the dosing interval is optimised to 8-12 weeks,” AstraZeneca said.

What the South African study actually showed

The study was a small-scale trial of 2,000 people aged 31 which showed the AstraZeneca vaccine had as little as 10% efficacy in preventing mild to moderate infection against the South African variant of Covid-19, B1351. However the researchers expressed hope the vaccine would still offer significant protection against more serious infection, which is the goal of the global vaccine program.

The study is yet to be peer-reviewed or published. The South African government has paused its planned rollout of the AstraZeneca vaccine in response.

It is not the only vaccine to show reduced efficacy against the South African variant. Trials of the Novavax vaccine also showed 60% efficacy against the South African variant, compared with an 89% efficacy overall – 95.6% against the original coronavirus and 85.6% against the UK variant.

Kelly said Australian authorities will be looking very closely at all information which comes out about the efficacy of the AstraZeneca vaccine, but said there was to date no information to suggest it did not protect against severe infections from the South African variant.

He said Australian authorities will be talking closely with the UK, where AstraZeneca has already been widely distributed.

“This is a very good vaccine, very safe, and once it goes through those processes, of safety, quality and efficacy, we will be able to look to roll out that vaccine as well – as always, subject to the TGA advice,” he said.

Yes, but it will take time. AstraZeneca said it has already started adapting its vaccine against the South African variant, “and will advance rapidly through clinical development so that it is ready should it be needed”.

Novavax responded to the lower results in South Africa by saying it would immediately start developing a new vaccine aimed specifically at the South African variant.

AstraZeneca is a viral vector vaccine, which relies on the use of an RNA molecule – the same part of the virus as used in the mRNA Pfizer and Moderna vaccines. Novavax is a more traditional protein-based vaccine, and they take longer to modify.

Kelly said mRNA and viral vector vaccines can be adapted more quickly than protein vaccines, but even if they are able to be adapted,” it is another issue to make nine billion of them”.

“If we’re going to vaccinate the whole world, it’s going to take time,” he said.

Why don’t we just all take the Pfizer vaccine?

That would be a great option, says McLaws. Except we don’t have enough, and there is significant pressure on the global supply. Australia recently secured an additional 10m doses of the Pfizer vaccine, taking the total contracted amount to 20m doses by the end of the year.

That’s enough to administer the required two doses to 10 million people, or just under 40% of Australia’s population. The first 80,000 doses of the Pfizer are still on track to arrive in Australia by the end of February, Kelly says, and authorities are hoping for weekly deliveries thereafter. People in the highest-risk cohort – frontline medical staff, hotel quarantine workers, aged and disability care home residents and staff – will get that vaccine.

The balance of the population is likely to receive either AstraZeneca, which is manufacturing 50m doses in Melbourne that are expected to be administered from March, pending TGA approval, or the Novavax vaccine, which is several months away.

What are the other options?

Well, we could mix vaccines. That concept is being trialled in the UK – they called for volunteers just last week – and will involve giving 820 unvaccinated people over the age of 50 a first dose of either the AstraZeneca or the Pfizer vaccine. Half the group will have their vaccine switched for the second dose, and the other half will get the same again.

It is an option worth considering, McLaws said. Without it, the risk is that people vaccinated with AstraZeneca – largely the 20- to 39-year-old cohort – may not be fully protected against Covid-19. That’s a problem because that age group, while not at highest risk of serious disease or death, made up half of all people who contracted Covid-19 in Australia last year. They are highly mobile and more likely to be underemployed and working multiple part-time jobs, which increases their risk of exposure.

Even without considering new variants, AstraZeneca has a lower reported efficacy than Pfizer and Novavax, the other options in Australia’s stable. It sought regulatory approval in the UK on the basis that it has about 70% efficacy.

“The risk is that if our 20- to 39-year-olds are vaccinated with AstraZeneca, we have at least a 30% risk of them not eliciting an immune response without the additional problem of a variant,” McLaws said. “This is an opportunity to look at how we protect the unknown 30-odd percent. And that may be to mix up the second dose with something that doesn’t have such low efficacy for the South African strain and the Brazilian strain.”

What does this mean for borders and other restrictions?

To date there have been no reported cases of the South African variant in the Australian community.

But the risk remains. Since Friday there have been 87 samples of B117, the UK variant, detected in hotel quarantine in Australia and 18 of B1351, the South African variant.

But the vaccine results solidify what epidemiologists have warned for some time: that life will not instantly go back to normal once the majority of the population has been vaccinated

https://www.theguardian.com/australia-news/2021/feb/09/astrazeneca-vaccine-why-australia-is-forging-ahead-as-south-africa-tackles-covid-variant