A ‘Special Communication’ article published within the journal JAMA Network Open provides an in depth overview of current high-quality literature describing the utility of face masks in reducing community-level transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative pathogen of the coronavirus disease 2019 (COVID-19) pandemic.

Special Communication: Masks During Pandemics Brought on by Respiratory Pathogens—Evidence and Implications for Motion. Image Credit: evrymmnt / Shutterstock

Background

Non-pharmacological control measures, including face mask-wearing, hand hygiene, physical distancing, and movement restrictions, had contributed significantly towards controlling the COVID-19 pandemic on the initial phase when medicines and vaccines against SARS-CoV-2 weren’t available out there.

In this text, scientists have summarized the high-quality data obtained throughout the pandemic regarding the advantages of face mask wearing in reducing the transmission of SARS-CoV-2, a respiratory virus known to spread between humans via large respiratory droplets and small respiratory aerosols.

Randomized controlled clinical trials

Two randomized controlled trials (RCTs) on face mask use in the neighborhood were conducted in the course of the COVID-19 pandemic.

The primary RCT was conducted in Denmark on 3030 people to research the protective efficacy of surgical masks in comparison with no masks. The findings were inconclusive, with participants from the intervention group (face masking during outdoor activities) showing only a non-significant reduction within the incidence of SARS-CoV-2 infection in comparison with the control group participants (no masking).

As mentioned by the scientists, other interventions might need diluted the actual effect of masking. One other possibility may very well be that the detected infections were spread mainly inside households, and thus, masking outside the house failed to supply the desirable protection against transmission.

The second RCT involving 600 villages in Bangladesh with greater than 340,000 residents found that wearing surgical masks in public places is related to a modest, statistically significant reduction in symptomatic SARS-CoV-2 infection. Surgical masks were found to be simpler than cloth masks.

A sufficient variety of RCTs on mask use couldn’t be done in the course of the pandemic due to ethical and feasibility issues related to randomizing people to masking or no masking. Furthermore, the time needed for designing, funding, and implementing RCTs further restricts their feasibility in the course of the pandemic. Other challenges include a scarcity of adherence by intervention group participants or the adoption of masking habits by control group participants.

Observational studies

There have been many high-quality case-control, cohort, and ecological studies conducted to judge the advantages of mask-wearing in the course of the COVID-19 pandemic. Developing simulation models of human respiration, scientists showed that cloth masks, surgical masks, and N95 respirators are highly effective in reducing the transmission of infectious respiratory droplets or aerosols.

Further evidence indicated that the protection against viral transmission is higher when each the source (infected person) and the exposed person are masked and that N95 respirators have higher protective efficacy than surgical masks because of upper filtration efficiency.

Observational studies have also highlighted the protective efficacy of masking in aircraft, schools, households, and communities. Aircraft, where people stay in close proximity for a chronic period in a poorly ventilated condition, function a possible hub for respiratory virus transmission. An outbreak of COVID-19 had occurred on the USS Theodore Roosevelt aircraft carrier within the early phase of the pandemic. A 30% lower risk of SARS-CoV-2 infection was observed amongst people wearing masks in the course of the journey.

In observational studies, a big problem is the influence of confounding aspects on the study intervention. In lots of COVID-19 outbreak conditions, masking was not the one implemented public health measure. This issue was addressed in studies by analyzing the outcomes after adjusting for other interventions (hand hygiene, isolation, physical distancing) or demographic features which will influence the infection risk.

Stratified analyses conducted in some studies indicated that the impact of masking on infection transmission will depend on the patterns of use, populations, and settings. In households, favorable outcomes were observed when the masking was performed in days before the onset of symptoms within the index case. This highlights the efficacy of masking in stopping asymptomatic infection transmission.

Overall, the findings of observational studies revealed comparatively higher effectiveness of masking amongst unvaccinated people, in addition to in outdoor conditions.

Mask mandates

The impact of mask mandates on infection transmission was analyzed in lots of studies. In Germany, mask mandates at different times in the course of the pandemic were found to be related to a forty five% reduction within the incidence of SARS-CoV-2 infection. A matched cohort evaluation of greater than 400 counties in the US showed a 25% reduction in SARS-CoV-2 infections 4 weeks after the mask mandate.

On the initial phase of the pandemic, there was a priority that community members who wear masks may develop a false sense of security and, thus, may avoid practicing other public health measures. Nonetheless, no scientific evidence is there in support of this issue.

A big pool of studies has shown that masking is a greater option than school closure when it comes to controlling infection spread amongst students and that college closure can have more negative impacts on students’ overall health and well-being.

Overall, the studies on mask use in the course of the COVID-19 pandemic highlight that face masking is an efficient public health measure in controlling the transmission of SARS-CoV-2. This information may very well be helpful for the preparedness of future epidemics or pandemics brought on by respiratory viruses.