The Victorian authorities used a “low high quality” masks examine to justify the mandate, specialists say | Victoria
A study that the Victorian government relied on to justify its strict mask mandate was criticized by some doctors and epidemiologists as “inferior” evidence.
While the experts stressed the importance of wearing masks indoors and that masks help reduce transmission, they said the “world’s first” joint study by the Burnet Institute and the Kirby Institute was flawed.
The study, published in July in the medical journal Plos One, used newspaper photos and surveys to assess mask compliance and its impact on Covid rates.
The mask mandate in Victoria has been controversial because it requires people to wear masks at all times, including outdoors in open spaces, despite strong evidence that the risk of transmission indoors, especially within households, is significantly higher.
In August, Prime Minister Daniel Andrews announced that Victorians would also not be allowed to remove their mask to drink alcohol outdoors, although it can be removed to eat or drink soft drinks. The Plos One study was used by the government to justify its policy, which applies even when people are walking outside with no people nearby.
The study analyzed images of people in public places from the digital archive of The Age newspaper, taken between July 10 and August 2, 2020 – before and after the introduction of masking requirements during the long state lockdown.
From these, all photos taken in public places in urban Melbourne, such as street landscapes and shopping malls, were used to calculate the proportion of people wearing masks in public over three time periods: May 10-19. July (the period before the announcement of the mandatory mask policy); 20.-22. July (period between the announcement and the beginning of the mask requirement); and 23 July to 2 August (mask must be worn). The researchers also conducted a survey.
The paper found that “mandatory mask use policy significantly increases the public use of masks and is associated with a significant decrease in new COVID-19 cases”.
In a press release from the Burnet Institute, it is said that the “world’s first” study showed that wearing masks turned the pandemic around “almost overnight” and was the most important tool in preventing the flood of Victoria’s second Covid wave of the year 2020 to turn.
“With the increasing evidence of outdoor transmission of the Delta variant, it is important that masks are worn both indoors and outdoors during a Covid-19 outbreak,” one author of the paper said in a press release that sponsored the study.
However, the study was called into question after news.com.au released concerns about the paper’s methodology. The news.com.au report said the Victorian Department of Health referred to the study as evidence of the mandate.
The researcher Dr. Kyle Sheldrick, who first raised concerns about the paper, said there were numerous methodological issues with the study.
“Drawing news photographer photos from a particular publication as a basis for causal inference is breathtaking,” said Sheldrick. “News photographers don’t go out and just randomly select people in the community, they are hired to take photos for certain stories and editorial lines. It’s hard to imagine a more biased sample. “
Sheldrick said there was a discrepancy between the methods described and the results reported and has publicly expressed his concerns.
“Although the newspaper’s archivist checked these two 14-day periods for additional unpublished photographs, which frankly adds very little, and analyzed all of the resulting images, the results of this search are never described and the authors describe only 44 in their results published pictures, ”he said.
Infectious Disease Doctor Prof. Peter Collignon agreed with Sheldrick, saying that observational studies were among the weakest study types. This is because they often fail to prove cause and effect; and there are too many “confounders” that are difficult to control but could affect the results.
“I think it was a mistake to use this study for any policy,” said Collignon.
“I think there are so many potential flaws in the methodology that this is not good quality evidence. If you want high-level evidence, you need to do randomized, controlled, double-blind studies. Well, this study is not, and by all evidence it would be considered inferior. “
An epidemiologist from Wollongong University, Gideon Meyerowitz-Katz, said the study was “not robust enough to establish a causal link between mask requirements, masking and a decline in Covid cases”.
“While the authors used two methods to derive an estimate of the change in masking behavior, neither gave a clear indication of how many people in the city or state wore masks over time,” he said. “The photos are media recordings and are not representative of the population. The survey was only conducted for a short period of time and only included 18 people after July 23rd. “
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However, he said a randomized controlled trial from Bangladesh found that mask guidelines may have a reasonable impact on cases, on the order of 10%. “So it’s important to note that flaws in a study don’t mean masks won’t work,” he said.
In a statement, the Burnet Institute, which provides models to the Victorian government, described Sheldrick as a “graduate student” and said it stood by the study.
“We accept that not everyone has to agree to our work … Others, including the peer reviewers of our paper, thought differently,” the statement reads.
“Our paper… showed that the introduction of the mask requirement in Melbourne was accompanied by a significant decrease in cases. The introduction of the directive was introduced in isolation from other restrictions, allowing for a unique assessment of its potential. That was unusual and the reason why we said at the time that it was a ‘world first’. “
Sheldrick said he was disappointed with the institute’s response.
“The answer doesn’t address specific criticisms like the fact that all ‘before’ photos are taken later in the afternoon, all ‘post-mandate’ photos before lunch, so there’s no way to really make sense of the two compare “, he called.
The epidemiology chair at Deakin University, Prof. Catherine Bennett, said the study was a useful contribution. She admitted that the researchers examined photos and data from “a very small time window” and assumed a linear relationship between masks and reduced Covid cases, “which is a bit unusual for an epidemic curve,” they had shown the mask policy transfer the adoption of the measure to the public.
“Following it up and ensuring that the directive changes practice in the community is a useful contribution,” she said.