Three years into the pandemic and hundreds of studies later, evidence is still lacking as to what extent masks may slow the spread of respiratory viruses such as flu or COVID-19, according to a research review published Jan. 30 in the Cochrane Library. Researchers said the findings underscore the need for more studies to definitively understand masking's benefits and are not intended to be a case against the practice.
For the review, Cochrane researchers examined 78 studies assessing the use of various mask types among more than 610,000 people in various settings in low-, middle- and high-income countries.
While some studies occurred during the 2009 H1N1 influenza and COVID-19 pandemics, many were conducted during flu seasons "in the context of lower respiratory viral circulation and transmission compared to COVID-19," researchers said.
When comparing the use of medical or surgical masks to no masks, the findings suggest that masks "will probably make little or no difference" on the number of flu or COVID-19 cases, researchers said. These findings were similar for studies conducted among healthcare workers wearing N95/P2 respirators.
Researchers cited many potential reasons for masking's lack of effect on virus spread, including poor study design, lower adherence to mask rules and the quality of masks used.
"Public health measures and physical interventions can be highly effective to interrupt the spread of respiratory viral infections, especially when they are part of a structured and coordinated programme that includes instruction and education, and when they are delivered together and with high adherence," researchers said. "Our review has provided important insights into research gaps that need to be addressed with respect to these physical interventions and their implementation and have been brought into a sharper focus as a result of the COVID-19 pandemic."
Read the full research article here.
Editor's note: This article was updated Feb. 10 at 3:30 p.m. CT.