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As Australia records its first cases of the much more infectious B117 coronavirus strain, medical experts have begun questioning whether the planned rollout of the AstraZeneca vaccine will be effective enough to generate herd immunity.
The Australian and New Zealand Society for Immunology said the federal government should immediately pause the planned rollout of the vaccine since phase three clinical trials show it is only 62 percent effective in preventing COVID-19, compared to the Pfizer and Moderna vaccines’ 95 and 94 percent efficacy, respectively.
“The AstraZeneca vaccine is not one I would be deploying widely, because of that lower efficacy,” the society’s president, Professor Stephen Turner, told the Sydney Morning Herald. “You cannot rely on it to establish herd immunity.”
“Given we have fantastic vaccines against this, I think it would be wise to not rely on the AstraZeneca vaccine for controlling the virus in Australia,” he said. “But it could be used as a tool to blunt the effect of COVID until those vaccines could be deployed.”
AstraZeneca is set to complete testing within a month, but medical experts doubt efficacy will increase to what is needed for herd immunity.
“Feels like Australia is being shortchanged with an inferior vaccine. Even with final AstraZeneca study results, the likelihood of anywhere close to 95 per cent efficacy is unlikely,” tweeted infectious diseases expert and associate professor Michelle Ananda-Rajah. “What is the endgame? Live with pulsed restrictions or thrive under immunity.”
Professor Dale Godfrey of the Doherty Institute told newsGP that even though the arguments for higher efficacy hold some validity, it in no way discredits AstraZeneca’s vaccine candidate.
“We really don’t have enough information to know where it will ultimately fall,” he said. “There are more trials underway, and it’s only through updated trials that we’ll have a much better idea about the actual efficacy of the AstraZeneca vaccine.”
Australia’s top health officer, Commonwealth Chief Medical Officer Paul Kelly, rejected calls to pause the rollout of the vaccine, telling Sky News that people should be very wary about using interim results from a phase three trial.
“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,” he said. “There was a range of studies reported on within [the Lancet] and the range of efficacy was from 62 per cent to 90 per cent. The full result was 70 per cent. That well exceeds what the [World Health Organization]” says is the minimum required for a vaccination.”
Australia has secured 10 million doses of the Pfizer vaccine, which will inoculate 5 million people, starting with frontline quarantine and health workers.
“The issue is that the rest of the country is going to be offered a lower efficacious vaccine – the AstraZeneca – and that’s just not going to confer herd immunity at a population level, we just don’t believe that based on our current data,” said Ananda-Rajah.
Research shows that on average every person infected with COVID-19 will infect between two and three other people. To achieve herd immunity vaccines needs to lower that average to below one.
The emergence of the much more contagious variant of COVID-19, B117, has made that all the more difficult and all the less likely that the AstraZeneca vaccine will be effective enough to stamp the virus out.
The B117 strain, which was first recognized in the United Kingdom and has since spread to at least 45 countries, is at least 50 percent more transmissible, but no more lethal than the original strain of COVID-19. Unfortunately, however, a more infectious virus could lead to many more deaths than a more lethal virus.
A hypothetical scenario published by the Council on Foreign Relations and the London School of Hygiene and Tropical Medicine shows that while “the more lethal strain initially causes more deaths, the more transmissible strain quickly outpaces it due to exponential growth in the number of infections.”
The hypothetical scenario shows that when each virus strain started from 10,000 infections, the 50 percent more lethal strain would lead to around 200 new deaths every six days, while the 50 percent more transmissible strain would lead to around 1,000 new deaths every six days. B117 also seems to infect younger people at a higher rate, too.
One of Australia’s largest cities, Brisbane, was last week plunged into a hard lockdown for three days after it was confirmed that a hotel quarantine worker who had been in the community had the B117 strain.
The case also prompted Australia’s national cabinet to announce that international arrival numbers would be halved and that a negative COVID-19 test must be recorded by all people seeking to travel to Australia.
Australia, most notably the state of Victoria, has already endured months of harsh stage four lockdown due to an outbreak of the original strain back in August. But modelling suggests that if B117 makes it into the community, not even that level of restriction will halt cases.
“Only strict 1st wave style Austria or New Zealand measures would be able to control B117 spread,” tweeted the author of the modelling, University of Calgary development biologist Malgorzata Gasperowicz. “The window of opportunity to get ahead of B117 is very narrow.”
The president of the Australian Medical Association, Dr. Omar Khorshid, told the Guardian that the new strain must not be allowed to enter Australia.
“This UK strain appears to be at greater risk of breaking out of hotel quarantine, and then spreading quickly to outrun and overwhelm our last lines of defence – physical distancing and testing and tracing.”
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