A new modelling study led by the University of Cambridge suggests that if facemasks are used across a population, it keeps the coronavirus ‘reproduction number’ under 1.0. When combined with lockdowns, widespread facemask use prevents further waves of the virus, according to the study, led by the University of Cambridge and published in the Proceedings of the Royal Society A.
The research suggests that lockdowns alone will not stop the resurgence of SARS-CoV-2. However, even homemade masks with limited effectiveness can dramatically reduce transmission rates if worn by enough people, regardless of whether they show symptoms.
The researchers worked to link the dynamics of spread between individuals with population-level models, to assess different scenarios of facemask adoption combined with periods of lockdown. The modelling included stages of infection and transmission via surfaces as well as air. Researchers also considered negative aspects of mask use, such as increased face touching.
The reproduction or ‘R’ number – the number of people an infected individual passes the virus onto – needs to stay below 1.0 for the pandemic to slow. The study found that if people wear masks whenever they are in public it is twice as effective at reducing ‘R’ than if masks are only worn after symptoms appear.
In all modelling scenarios, routine facemask use by 50% or more of the population reduced Covid-19 spread to an R less than 1.0, flattening future disease waves and allowing less-stringent lockdowns. Viral spread reduced further as more people adopted masks when in public. And 100% mask adoption combined with on/off lockdowns prevented any further disease resurgence for the 18 months required for a possible vaccine.
The models suggest that a policy of total facemask adoption can still prevent a second wave even if it isn’t instigated until 120 days after an epidemic begins (defined as the first 100 cases).
The team investigated the varying effectiveness of facemasks. Previous research shows that even homemade masks made from cotton t-shirts or dishcloths can prove 90% effective at preventing transmission. The study suggests that an entire population wearing masks of just 75% effectiveness can bring a very high ‘R’ number of 4.0 all the way down to under 1.0, even without aid of lockdowns. —Source: University of Cambridge