Masks and physical distancing are effective, study concludes

• Of all the millions of dollars hurriedly invested in COVID-19 research since the start of the pandemic, most of it has been dedicated to medicines and vaccines rather than public health and social measures (PHSMs).
• PHSMs include mask-wearing, physical distancing, hand washing, lockdowns, and closures.
• However, a review of key research supports the value of physical distancing and mask-wearing as ways to avoid SARS-CoV-2 infection.

While researchers worldwide have produced vaccines and other pharmaceuticals with unprecedented speed, 31% of research awards — totaling 4.1% of tracked research funding — have gone into measuring the effectiveness of PHSM that health experts recommend for avoiding SARS-CoV-2 infection.

PHSMs include everyday personal behaviors such as physical distancing, mask-wearing, and hand washing. On a community scale, they include lockdowns, border closures, and business and school closures.

Researchers have just released a review of existing research exploring the value of personal PHSMs.

The meta-analysis of existing research found that mask-wearing led to a 53% reduction in the incidence of SARS-CoV-2 infections, while physical distancing was associated with a 25% reduction.

The published paper appears alongside an editorial featuring authors led by Prof. Paul Glasziou of Bond University in Australia. In it, they question these high percentages.

An issue with quality

The authors screened 36,729 studies. Of these, 72 met the inclusion criteria, such as being the right study type and published in English. The latter is a limitation of the review, given the international nature of COVID-19 research. Of the 72, only 35 studies attempted to measure the effectiveness of individual PHSMs.

Of the 35, just one study was a randomized controlled trial — the rest were observational studies of often questionable quality and scale.

Dr. Stella Talic, of Monash University in Melbourne, Australia, lead author of the study, explained to Medical News Today:

“Population studies are valuable tools to assess a range of public health issues, but are generally not the best way to measure interventions’ effectiveness, as they cannot directly assess causation.”

In 24 of the studies, the analysis revealed moderate result-skewing bias, with seven others exhibiting high-to-serious bias. The researchers ultimately included just eight of the 35 studies in the meta-analysis.

They found that “Owing to [the] heterogeneity of the studies, meta-analysis was not possible for the outcomes of quarantine and isolation, universal lockdowns, and closures of borders, schools, and workplaces.”

Dr. Talic explained the difficulty of assessing such PHSMs:

“It would be very hard to measure those interventions individually, but I believe that more natural experiments and quasi-randomized controlled trials are needed in order to assess those measures. We also need to be mindful of the negative effects that those more stringent measures have on the wider populations. Those effects should also be addressed in future studies so that we can clearly weigh the benefits against the risks in different populations.”

The study appears in The BMJ.

Difficult to separate

One of the difficulties in assessing personal PHSM interventions is that any one of them may be a marker of a type of person who practices them all.

This potential confounding was one of the primary sources of bias in the findings of the studies. In addition, the authors write:

“Variations in testing capacity and coverage, changes to diagnostic criteria, and access to accurate and reliable outcome data on COVID-19 incidence and COVID-19 mortality was a source of measurement bias for numerous studies.”

’A pandemic tragedy’

The subheading of the associated editorial reads: “Lack of good research is a pandemic tragedy.” In it, the authors write:

“Although the pandemic has seen remarkable trials for vaccines and drug treatments, much less has been done to evaluate the effects of PHSMs.”

However, the authors of the editorial note that there were two significant randomized trials not included in the meta-analysis. One of which, conducted in Bangladesh, is available as a pre-print. Another, which researchers carried out in Guinea-Bissau, is yet to be published.

“Positive news,” said Dr. Talic, “is evidence from two randomized controlled trials that confirms that there is an effect in wearing masks, albeit smaller than the ones found in observational studies.”

The editorial notes that “[c]ombined, these two randomized trials suggest that mask-wearing is responsible for a statistically significant relative risk reduction of about 10% in incidence.” This is substantially lower than the 53% that the main analysis finds.

Still, says the editorial, the lack of PHSM research so far is the result of a “puzzling” lack of adequate funding given PHSMs’ claimed benefits. The authors describe the quality of existing research as:

“Low or very low, as it consists of mainly observational studies with poor methods (biases in measurement of outcomes, classification of PHSM, and missing data), and high heterogeneity of effect size.”

Despite this, health experts may soon understand the puzzle better, according to the editorial, thanks to an ongoing major survey by the University of Oslo, asking respondents to identify the “key barriers to trials of PHSMs and how best to overcome them.”

The editorial authors are also heartened by the World Health Organization’s (WHO) recently stated aim to strengthen “the global evidence base to provide actionable and evidence-informed guidance on such measures for decision-makers.”

Dr. Talic supports the editorial’s position, saying:

“I most definitely agree with Prof. Glasziou and other colleagues — we need better evidence to inform policy-decision making and, more generally, we need more investment into global public health to inform future pandemic responses.”

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