Are masks effective in the protection against COVID-19?

By Tarun Sai LomteReviewed by Lily Ramsey, LLMMay 17 2023

A recent editorial published in the Annals of Internal Medicine Journal discussed the efficacy of masks in preventing coronavirus disease 2019 (COVID-19).

Study: Getting to the Truth About the Effectiveness of Masks in Preventing COVID-19. Image Credit: DrazenZigic/Shutterstock.com

Background

Masks were just the devices to prevent respiratory infections before the COVID-19 pandemic. However, masking recommendations were different during the pandemic and had become politically contentious.

As such, many studies analyzed the physical properties of masks; but they were small, often involving robotic wearers. Moreover, they only studied the spread of particles instead of infection.

Several observational studies suggested that masking was associated with reduced COVID-19 incidence in communities. Still, it remains difficult for these studies to determine whether it was due to masking, or physical distancing, among other measures.

Only three trials have investigated the efficacy of masking in reducing the incidence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in real-world scenarios.

Evidence on masking effectiveness

Although trials offer high-quality evidence, the evolution of the pandemic, accompanied by the changes in immunity, vaccine availability, and SARS-CoV-2 variants, presents challenges to definitively answer questions about the efficacy of masks in averting infection.

A systematic living review concluded that masking interventions might be associated with a slight decline in SARS-CoV-2 infection risk in community settings, with a similar risk using N95 respirators or surgical masks in healthcare settings.

Another systematic review focused on physical interventions to decrease respiratory viral infections and reported that masking in the community caused no or little change in the spread of COVID-19-like or influenza-like illness.

There was a lack of evidence on the potential harms related to masking inventions in both reviews. Although both are systematic assessments of the available evidence, they reported substantial uncertainty and evidence gaps.

Considerations

Some people say masks are effective, while others state they are ineffective. First, whether people refer to preventing infection or blocking the passage of the virus must be clarified, whether they mean the efficacy of masks per se or of masking policies or recommendations.

Second, masking must be considered an element of multicomponent strategies to decrease the spread of infection.

In addition, potential harms and benefits associated with masking should be explicitly considered. This is because some may justify masking based on any evidence of benefits, while others believe that discomfort, communication impedance, and inconvenience due to masks outweigh the small benefits. Real-world assessment of the effectiveness of masks is essential.

Studies should assess clinically significant outcomes because masking is recommended to prevent the spread of infection. Masking recommendations occur along with other concurrent measures for infection control.

Therefore, studies should also account for these contemporary measures. Additionally, realist and process evaluation trials may be adopted to inform the conditions for masking to work.

Concluding remarks

Although evidence suggests that masks could work in averting COVID-19, there are substantial gaps, and it is necessary to fill them with more evidence in the context of potential viral outbreaks in the future.

Further, designing studies to synthesize and interpret evidence on masking interventions more accurately is imperative, realizing the possibility that the truth about when masking benefits outweigh the potential harm could never be definitively reached.