Reducing Risk, One Mask at a Time: What the Science Says

A few items bring back unpleasant memories of COVID-19, such as masks. However, they are among the simplest and most effective ways to prevent the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). If everyone had worn them correctly, the transmission could have been reduced as much as ninefold, according to a theoretical study published in Physical Review E by Richard P. Sear, PhD, from the University of Surrey, Guildford, England.

Study Overcomes Limitations

This study aimed to address the limitations of epidemiological investigations of masks, which can be complex and error-prone. Sear used data obtained from the UK’s COVID-19 app, totaling 7 million contacts, to create a mathematical model of virus transmission, focusing on the correlation between contact duration and infection. The model estimates that if all UK residents had worn masks during every potential exposure, virus transmission would have been approximately nine times lower.

Although this is a mathematical model, it adds to the growing evidence that supports the benefits of masks. Masks are among the best strategies for treating SARS-CoV-2. This conclusion has been supported by several systematic reviews and additional statistical studies. Conversely, the decision to relax and eliminate mask regulations has had consequences that have received little attention.

As expected, removing the mask mandate leads to increased virus transmission, resulting in more hospitalizations and deaths. A 2024 study estimated that in Japan, where cultural factors lead to much higher mask use in public than in Europe, the decline in mask use from 97% of the population in 2022 to 63% in October 2023 may have caused an additional 3500 deaths.

Impact Beyond SARS-CoV-2

One remarkable effect of non-pharmaceutical interventions during the pandemic was the probable extinction of an entire influenza strain (B/Yamagata), which could improve future influenza vaccines and significantly reduce the spread of respiratory syncytial virus. While this was not solely due to masks, it was also influenced by emergency measures such as lockdowns and social distancing. These behavioral changes can positively alter the landscape of infectious diseases.

Masks play a role in reducing influenza transmission during pandemics. Their effectiveness has been supported by several studies and systematic reviews on a wide range of respiratory viruses. A randomized clinical trial involving 4647 Norwegian participants from February to April 2023, published in May 2024 by the British Medical Journal, suggested that wearing a mask reduces the incidence of respiratory symptoms. Specifically, 8.9% of those who wore masks reported respiratory symptoms during the study period compared with 12.2% of those who did not, representing a relative risk reduction of 27%.

Widespread mask use could also protect against other factors such as fine particulate matter, indirectly reducing the risk for various health conditions. A retrospective study involving 7.8 million residents in the Chinese city of Weifang, published in December 2024 by BMC Public Health, suggested that mask use during the pandemic may have also protected the population from pollution, reducing the number of stroke cases by 38.6% over 33 months of follow-up.

Although there are still voices in bioethics calling for the reintroduction of mask mandates in public places, it is unlikely that, barring emergencies, mask mandates are politically and socially acceptable today. Mask use is also considered a politically polarizing topic in several Western countries. Nevertheless, it is worth considering whether, as we move away from the acute phase of the COVID-19 pandemic, we can more objectively promote the use of masks in public places.

Communicating the importance of public health initiatives and persuading people to support them is a well-known challenge. However, scientific literature offers valuable insights. These include encouraging people to rely on rational thinking rather than emotions and providing information on how masks protect those around them. The fact that East Asian cultures tend to have a more positive relationship with the use of masks shows that, in principle, it is possible to make them acceptable. Data from studies indicate that, even in light of future pandemics, it may be time to break the polarization and bring masks back — not as a requirement for everyone but as a choice for many.

This story was translated from Univadis Italy using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.