Drug company Pfizer announced overnight that its COVID-19 vaccine may be 90 per cent effective in stopping the virus but it’s not at the finish line yet.
The Pfizer trial is one of four potential vaccines the Australian Government has signed an agreement to purchase if it is successful.
Here are five things you need to know about this announcement.
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What exactly have they announced?
Drug companies Pfizer and BioNTech announced their vaccine candidate was “more than 90 per cent effective in preventing COVID-19” in people who, as far as they knew, had not previously been infected with the virus.
The vaccine, dubbed BNT162b2, involves two jabs, each three weeks apart.
In interim results from the companies’ phase 3 clinical trial, which started in July and has more than 43,000 enrolled participants, they reported 94 lab-confirmed COVID-19 infections.
What does 90 per cent ‘effective’ mean?
It sounds pretty good, hey?
But the vaccine’s ‘efficacy’ doesn’t measure how well it stops the SARS-CoV-2 virus entering a vaccinated person’s body.
Instead, it’s a measure of stopping or at least reducing the severity of COVID-19 symptoms.
And this vaccine apparently does just that, nine times out of 10.
Kylie Quinn, a vaccine expert at RMIT University, told ABC News, “if you had 10 people who you knew were going to be infected with (COVID-19), and you vaccinated those people before they were exposed, nine out of those 10 people would not get the infection anymore”.
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If you want to get technical (and who doesn’t?!), vaccine efficacy and vaccine effectiveness are slightly different terms.
Vaccine efficacy is calculated through clinical trials, like the Pfizer/BioNTech trial. Vaccine effectiveness is measured out in the real world, once the vaccine has been approved for use in the general population.
To calculate the more-than-90-per-cent efficacy figure for BNT162b2, an external committee examined how many of the 94 infected individuals were vaccinated and how many received the placebo (a saline injection).
But the published results are a little light on detail. The announcement was made via press release not a peer-reviewed journal paper and it did not include the vaccine/placebo breakdown of infected participants.
The efficacy of the vaccine may change over time, too.
Dr Quinn says there’s still a little way to go before the trial wraps up.
“This is the interim analysis of 94 patients. The study closes out at 164 individuals who have become symptomatic,” Dr Quinn says.
“So we’re not far enough.”
Does this make it the vaccine front runner?
It sure does but others are likely to be hot on its tail.
There are currently 11 COVID-19 vaccines in Phase 3 clinical trials, but Pfizer is the first company to announce its results.
While Pfizer is still collecting safety data on the vaccine, it says so far no serious safety concerns have been observed. It plans to apply for emergency authorisation from the US Food and Drug Administration in late November.
Clinical trial stages
- Pre-clinical: Testing in animals. Does the vaccine produce antibodies? Does it protect against illness? What dose is necessary?
- Phase I: Testing in a small number of humans. This phase is about making sure the vaccine is safe.
- Phase II: More testing in humans does the vaccine actually work?
- Phase III: Testing in a larger number of humans to confirm its effectiveness.
- Phase IV: After the vaccine has been rolled out, ongoing surveillance to make sure it’s safe and doesn’t have long-term adverse effects.
The early trial results aren’t just good news for Pfizer either, according to Dr Richard Hatchett, CEO of the Coalition for Epidemic Preparedness Innovations (CEPI).
“We believe these interim results also increase the probability of success of other COVID-19 candidate vaccines which use a similar approach,” Dr Hatchett said in a statement.
That approach is targeting the SARS-CoV-2’s spike protein, the pointy bits on the surface of the virus that allow it to enter our cells.
We were pretty sure it was the right target for vaccines, but these results clinch it, says Professor Nolan.
“While there was every reason to believe that it was the right target, we were never going to know for sure until we had this sort of human response data,” Professor Nolan says.
“So clearly, the spike protein is the right target, and that means it’s more likely than not that there will be several successful vaccines.”
Moderna, which is also working on an mRNA vaccine, should be releasing efficacy results “in the next couple of weeks”, Professor Nolan says.
He says the Oxford/AstraZeneca vaccine, which Australia also has an agreement to distribute if it proves safe and effective, will also be close to revealing results. In September this trial was paused when some participants had adverse events, but the pause has since been lifted.
What’s everyone saying about it?
The data, while preliminary, has been enthusiastically welcomed by infectious disease and public health experts around the world, including White House coronavirus adviser Dr Anthony Fauci, who said the 90 per cent effectiveness result was “just extraordinary”.
“Not very many people expected it would be as high as that,” he says.
“It’s going to have a major impact on everything we do with respect to COVID.”
Dr Bruce Aylward, the World Health Organisation’s senior adviser, says Pfizer’s vaccine could “fundamentally change the direction of this crisis” by March, when the UN agency hopes to start vaccinating high risk groups.
But independent scientists, including leading vaccine developer Dr Stanley Plotkin, have also cautioned against banking on the results too soon, noting that the data are incomplete and that many questions still remain.
At this stage, no long-term safety and efficacy data has been collected, and it will take months if not years to understand how long immunity (generated by the vaccine) lasts.
“That there is early efficacy of 90 per cent is great, but … we don’t know whether vaccine protects against infection, so that individuals who are vaccinated won’t be able to excrete the virus and infect other people,” Dr Plotkin, emeritus professor of paediatrics at the University of Pennsylvania, told RN Breakfast.
“We don’t know whether it protects the elderly as well as the young.
“As a scientist I would have to wait for those other data before I could decide whether or not this is really as promising as it sounds.”
There is also concern the vaccine will present significant manufacturing and logistical challenges, points out Terry Nolan, a vaccine expert from the University of Melbourne’s Doherty Institute.
Like other vaccines made with mRNA which carry instructions to the body using genetic material the vaccine needs to be stored at ultra-cold temperatures, in this case, below minus 80C.
“They’re thawed before they’re given, of course, but they’re not stable for a long period of time at refrigerator temperature,” Professor Nolan says.
“The distribution between the warehouse and then a clinic or a GP surgery or wherever else it’s going to be given, and how it’s stored that’s going to be the hard bit.
“I suspect the [Australian] Government won’t be announcing that just yet, I suspect they’ll be working on a solution to make sure that is going to work.”
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When would we get it in Australia?
The Pfizer trial vaccine is one of four potential vaccines the Australian Government has signed an agreement to purchase if it is successful, and Federal Health Minister Greg Hunt says the Government would continue to monitor results.
“The data on our vaccine candidates continues to be positive. We will examine the evidence carefully but the latest results are heartening news.”
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Last week, secretary of the Department of Health Brendan Murphy said that because the vaccine involved complicated technology (an mRNA vaccine has never been successfully manufactured and distributed anywhere in the world), the Australian Government had decided to buy a small number of doses as a first option.
“If this turns out to be the most successful vaccine, obviously there’s a capacity to buy more,” he said.
“And there is the capacity, we are exploring the potential, of whether we could set up local manufacturing, but that isn’t a prospect at the moment.”
As for when Australians can expect to be rolling up their sleeves to get a COVID-19 jab, Minister Hunt has previously said the goal and expectation is that “Australians who sought vaccination will be vaccinated within 2021”.
If Pfizer’s trial vaccine is approved, the company says it aims to supply 1.3 billion doses of the vaccine by the end of 2021.
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