How many Australians need to get the coronavirus vaccine to stop the outbreak? And what if it doesn’t work?

How many Australians need to get the coronavirus vaccine to stop the outbreak? And what if it doesn't work?

The Federal Government has secured the rights to manufacture millions of doses of the so-called “Oxford vaccine” — a viral vector vaccine that effectively mimics the coronavirus and trains the immune system to fight back.

Lauded by Prime Minister Scott Morrison as “one of the most advanced and promising in the world”, the development is another step towards the coronavirus finish line.

But its effectiveness could hinge on a number of factors.

Prime Minister Scott Morrison next to a man holding a vaccine vile
The vaccine was lauded by Prime Minister Scott Morrison as “one of the most advanced and promising in the world”.(AAP: Lisa Maree Williams)

How many people need to get it for it to work?

Addressing the announcement on Wednesday, Mr Morrison was clear: “We’ll need about a 95 per cent vaccination rate across the country.”

“That is the normal target range for when you’re having a vaccination program,” he said.

“And we’ll be seeking to ensure that is widely implemented with our partners around the country.”

However, not all vaccines are created equal, and the level of protection they provide is just as important as the number of people who agree to take part.

One study, published in the American Journal of Preventative Medicine, found the effectiveness of a coronavirus vaccine may have to be as high as 80 per cent before people can safely stop relying on social distancing.

“If 100 people who haven’t been exposed to the virus are given a vaccine that has an efficacy of 80 per cent, that means that on average 80 of them would not get infected,” noted Bruce Y Lee, a professor of health policy and management at the University of New York.

By comparison, the measles vaccine has an efficacy of about 95 per cent to 98 per cent, while the flu vaccine has been found to range between 20 per cent and 60 per cent.

So how effective is the Oxford vaccine?

The short answer is, we’re not entirely sure.

Described as a “frontrunner” in the battle against COVID-19, one study — published in The Lancet in July — found the vaccine stimulated the right kind of immune response.

But questions remain around how long the vaccine, which is being developed by pharmaceutical giant AstraZeneca, could provide immunity.

“We’ve got no idea whether the vaccine, whether that response in the body continues after the first couple of months,” says Stephen Duckett, a health economist at the Grattan Institute.

“They didn’t report that in their in their in their study. And it may, it may not.”

Writing for The Conversation, Oxford immunologist Rebecca Ashfield herself noted that it is essential to follow the vaccine-induced immune response “over a period of at least one year to estimate whether booster injections will be required, and if so how often”.

Moreover, the vaccine is yet to be tested on vulnerable groups and still needs to pass through phase 3 trials.

But these large-scale trials, in which thousands of people from the UK, Brazil and India will be immunised, are looking “promising”, Duckett says.

Read more about coronavirus:

How many Australians will get the vaccine?

While Mr Morrison has back tracked away from language about the vaccine being mandatory, it is expect that vaccination will be strongly encouraged by the Government.

It’s hard to predict at this stage how that will translate into national uptake, both in terms of how quickly that many doses are available and whether the public will embrace it.

Prime Minister Scott Morrison wearing a mask.
Mr Morrison has back tracked away from language about the vaccine being mandatory.(AAP: Lisa Maree Williams)

Deputy Chief Medical Officer Nick Coatsworth was optimistic that the Australian public would embrace an eventual vaccine rollout, especially since this year’s flu vaccine was so well received.

“The rates of flu vaccination this year have been astonishing. I have never seen them in my practising career, they’ve been so high,” he said.

In 2019 — before coronavirus emerged — 12.5 million flu shots were available to Australians, half the number of Oxford vaccine on order.

More than 90 per cent of parents vaccinate their children by two years old with the 95 per cent target almost achieved by the time they turn five.

Who might not be able to get it?

To date, the Oxford vaccine has only been tested on healthy adults between the ages of 18 and 55.

But an expanded UK trial will include children and older adults — including those over 70 and children aged between 5 and 12 — to estimate vaccine efficacy in these age groups.

Nurse injects vaccine into arm
To date, the Oxford vaccine has only been tested on healthy adults between the ages of 18 and 55.(ABC News: Aneeta Bhole)

Similarly, a clinical trial currently underway in South Africa includes an arm involving 50 people living with HIV.

But how it will effect these demographics is yet to be seen. It’s also not clear that the vaccine could be extended to those who are pregnant, breastfeeding or immunosuppressed — groups that aren’t usually able to have “live” vaccines and the reason why herd immunity is so important.

Asked who may receive the vaccine first should it be rolled out across Australia, Mr Morrison pointed to “more vulnerable parts of the community”.

But he noted it “will be dependent on the medical issues that might present with some of those cohorts”.

Is the ‘rushed’ vaccine process turning people off?

With about 160 vaccines currently in development, some are understandably sceptical.

Russia’s decision to bypass phase 3 of clinical trials for its Sputnik V vaccine, for example, was labelled “reckless” by Australian researchers and prompted caution from the World Health Organisation.

Russia approves vaccine for COVID-19 after two months of testing

But aside from the risks posed to participants who receive a vaccination that has not been tested for effectiveness or safety on a large scale, researchers fear any adverse effects could further galvanise the anti-vax movement.

“There’s already a lot of distrust around vaccines, so you definitely don’t want to put something out there which ends up harming people,” says Narcyz Guinea, who researches the regulation of biomedical innovation at the University of Sydney’s School of Public Health.

“Even if it’s only a small proportion…[it] increases that distrust.”

What do we do if the vaccine doesn’t work?

It is, undoubtedly, the elephant in the room: What if the vaccine all comes to nothing?

During Wednesday’s announcement, Acting Chief Medical Officer Paul Kelly emphasised that the agreement with AstraZeneca was only the “first step”.

“These so-called pre-purchase agreements, as well as looking at funding our own research and development here in Australia… but also partnering with other vaccine [developers]. That’s part of our strategy.”

Until an effective vaccine is found, however, Mr Morrison has cautioned Australia must “continue to live positively with the virus, to ensure that we can establish our economy as much as is normally possible.”

“We are working towards and hoping for and planning and preparing for a vaccine,” he said.

“But equally, at the same time, you need to ensure that you can reopen your economy and you can get on top of the outbreaks that are there.”

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