Liam Mannix’s Examine newsletter explains and analyses science with a rigorous focus on the evidence. Sign up to get it each week.
The Burnet Institute stood by the study.
“Over a year later than this work was done, there is a huge body of international work supporting the use of face masks which is presumably why essentially virtually all jurisdictions in Australia and around the world adopt them,” a spokeswoman said.
The study used a sample of 44 photos, mostly taken in the CBD between July 10 and August 2. About 43 per cent of people photographed before the mask mandate were wearing one. After the mandate, that rose to 98 per cent.
However, Mr Bevens pointed out they were likely not representative of Melbourne as a whole.
“Is it appropriate to compare people at Flinders Street at 8.30am before the mask mandate to those there at 2pm after the mandate has been brought in?”
Another potential confounder: all the pre-mandate photos were taken in the afternoon, and all the post-mandate photos were taken in the morning.
The supporting survey’s sample size was extremely small: just 104 Victorians over four days were asked about their mask use after the mandate was implemented.
“I don’t think we could conclude much from this study. Unlike other recently published RCT [randomised controlled trial] data, it doesn’t really tell us anything about whether masks work,” said University of Wollongong epidemiologist Gideon Meyerowitz-Katz.
A Monash University study of Victoria’s second wave, to be published in Nature Communications in coming days, reaches the same conclusion: masks were the single most effective intervention in turning around Victoria’s epidemic.
The Monash study relied on a separate YouGov survey that showed even higher levels of mask compliance following the mandate, said Professor Trauer.
The Monash study was co-authored by Chief Health Officer Professor Brett Sutton and funded by the Victorian Department of Health. Professor Trauer regularly collaborates with the Burnet Institute.