2019 WHO review of mask studies found 'no evidence' they stopped transmission of flu

A 2019 World Health Organization review of numerous studies testing the efficacy of face coverings to stop the transmission of influenza found "no evidence that [wearing a mask] is effective in reducing transmission" of the virus. The organization has further discouraged individuals from using cloth masks to cover their faces during pandemics, though at times that advice has appeared to shift.

The 2019 review was part of a larger study examining "non-pharmaceutical public health measures for mitigating the risk and impact of epidemic and pandemic influenza." That paper effected a "systematic review of the evidence on the effectiveness of [non-pharmaceutical interventions], including personal protective measures, environmental measures, social distancing measures and travel-related measures." 

Among the measures the study reviewed were hand-washing, quarantine protocols, school closures, "respiratory etiquette" and face masks. 

The document reviews 10 separate randomized, controlled trials examining the effectiveness of face masks in stopping flu transmission. There was "no evidence that face masks are effective in reducing transmission of laboratory-confirmed influenza" found in that survey. 

Of the surveyed studies, just two found any reduction at all in the rate of influenza-like illnesses among participants; in one, the reduction occurred over a two-week period during a five-month study, while reductions in another "were not statistically significant."

The review's authors note that "the majority of these studies were conducted in households in which at least one person was infected, and exposure levels might be relatively higher." Therefore, "additional studies of face mask use in the general community would be valuable."

Though the organization conceded little evidence for the effectiveness of face masks, in an overview of the paper they nevertheless "conditionally" recommend them for the broader public in the case of "severe epidemics or pandemics."

"Although there is no evidence that this is effective in reducing transmission, there is mechanistic plausibility for the potential effectiveness of this measure," the overview reads. 

WHO gives shifting advice on cloth masks 

The World Health Organization made headlines over the summer when it advised governments to begin recommending that individuals wear face coverings in certain situations such as public transport and other crowded public venues. 

In June, the organization cited "a growing compendium of observational evidence on the use of masks by the general public" as its reason for shifting its advice, though the organization still conceded that there is "no direct evidence (from studies on COVID- 19 and in healthy people in the community) on the effectiveness of universal masking of healthy people in the community to prevent infection with respiratory viruses, including COVID-19."

That guidance, along with a growing push for more and more individuals to wear masks while out in public, has over the past several months led to widespread mask mandates in countries across the world. Many individuals have taken to wearing cloth masks either as a personal choice or to comply with local mandates. 

Many of those masks have been homemade, though booming corporate and cottage industries in cloth mask manufacturing have arisen over the last several months. 

Yet the World Health Organization itself gives shifting advice on cloth masks. In its 2019 literature review it stated bluntly: "Reusable cloth face masks are not recommended." In its guidance over the summer, however, it gave detailed technical standards by which individuals might fabricate their own cloth face coverings. Yet in that document it also stated that the "limited available evidence" in favor of cloth masks made them inadvisable for health care workers. 

On its website, meanwhile, the WHO states that it "does not recommend [the] widespread use [of cloth face masks] among the public for control of COVID-19." Yet in the same paragraph it argues that governments should "encourage the general public to use non-medical fabric masks" in "areas of widespread transmission, with limited capacity for implementing control measures and especially in settings where physical distancing of at least 1 metre is not possible."

The WHO did not answer queries from Just the News regarding its recommendation to wear face masks.

COVID and influenza spread the same way

Though the WHO's literature review of mask effectiveness took place prior to the COVID-19 pandemic, its findings could offer important implications for mask usage as applied to the current viral crisis. 

Experts assert that COVID-19 spreads primarily through respiratory droplets from infected individuals. Masks, including cloth face masks, are meant to stop those droplets from spreading to other individuals and to surfaces. 

Yet influenza spreads the same way, according to medical experts. "Most experts think that flu viruses spread mainly by droplets made when people with flu cough, sneeze or talk," the Centers for Disease Control and Prevention says on its website.

Whether or not the ostensible ineffectiveness of face masks in stopping influenza can be extrapolated to COVID-19 is currently unknown. Many U.S. states months ago mandated that citizens wear masks while out in public, yet many of those same states — such as Michigan, California, Washington and others —have seen sustained or increasing infection rates since the mandates went into effect.