Herd immunity is a myth, infectious disease experts warn
Helen Pitt and Jenny Noyes12:59, Apr 22 2020
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If a country were to lift all restrictions in the pursuit of herd immunity it should expect cycling epidemics of Covid-19, increased absenteeism, and ultimately more deaths, one of Australia's leading pandemic experts has warned.
Infectious disease expert Professor Raina MacIntyre issued the warning on Tuesday in a Covid-19 pandemic update at the University of New South Wales' Kirby Institute – the first to collate data from international medical journals and universities since the disease was identified in Wuhan, China in December 2019.
Professor MacIntyre, who is head of the Biosecurity Research Programme at the institute, spoke of the "myth of herd immunity" – exposing a population to the virus for the purposes of building up natural immunity and sacrificing the vulnerable.
"It does have a connotation of eugenics," she said. "What you will see is a large increase in cases for little gain because probably by the time you get to about 20 to 30 per cent of the population impacted, you'll start putting the brakes on and having more lockdowns because the health system will be too severely impacted.
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"We'll have these cycling epidemics, large proportions of absenteeism from work and see the full spectrum of disease – as has been seen in the US, the UK, Europe and China – which is that you are seeing deaths in children, infants and young people," she said.
"You'll start to see healthcare workers dying as they are dying in those countries ... that will impact your capacity to treat other conditions. If half your workforce is off sick or in quarantine because you're having a massive outbreak in your hospital, you may not be able to get treatment if you turn up with your myocardial infarction," she said.
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Herd immunity is not a strategy the Australian government is pursuing. Instead all states and territories are on a containment or elimination trajectory.
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Medical professionals administer Covid-19 tests at the Bondi Beach drive-through testing centre.
But Professor McIntyre's comments follow days of public debate about whether the economic hardships caused by Australia's current restrictions, implemented to protect the elderly and vulnerable, impact too heavily on the young and healthy.
Professor of Infectious Diseases at Australian National University Peter Collignon said herd immunity in Sweden did not seem to be working, however he did think students should be returning to schools in Australia.
"If this were influenza I'd be closing schools but all the data seems to suggest this infection is very uncommon in the under 15 age group, schools are probably one of the safest workplaces you can go," he said.
"But I am worried about a second wave of infection in winter: in two months we might be seeing a ripple of new infections, not a tsunami," he said.
Associate Professor Adam Kamradt-Scott, at the University of Sydney's Centre for International Security Studies, agreed herd immunity is a risky strategy.
"At the moment we don't know how long the length of immunity is for SARS-CoV-2 will be. We also don't know whether there might be very minor mutations that would see a slightly different strain start to circulate. If that was to occur, we don't know yet whether previous exposure would provide sufficient immunity," he said.
"We are making a lot of educated guesses at the moment based on previous pandemics but the fact is we haven't faced something like this in more than 100 years."
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