"No RCT for Masks? No Problem
— Other forms of evidence are available to judge effectiveness of this and other interventions
...But what constitutes evidence in this context? There has been an almost exclusive focus on evidence from experimental studies, specifically the randomized controlled trial (RCT), which is characterized as the "gold standard" of research, as it allows for the determination of causality. However, the reason such evidence is still lacking, should be obvious – the RCT is neither feasible nor appropriate for determining the effectiveness of mask-wearing in the community in protecting against COVID-19, and moreover, its use will be considered unethical in the context of a deadly pandemic. At the minimum, an RCT would require manipulation of the intervention, by way of the researcher randomly assigning some members of the community to wear a face mask and others not to, and ensuring that both community groups are similar, based on key background characteristics, in other words, controlling for potential confounding factors.
An RCT may be theoretically perfect, but it is certainly not realistic in the context of mask-wearing and the COVID-19 pandemic. What is more relevant, meaningful, and available, is evidence from the observational research spectrum, primarily natural experiments. A natural experiment is an observational study where an intervention such as mask-wearing was implemented by forces outside the researcher's control, such as a governmental mandate, and the outcome (level of COVID-19 infection) can be used to explore a specific research question, for example: Does mask-wearing in the community setting reduce the level of COVID-19 infection? The results can be evaluated for causal inference, using a common epidemiological model known as the Bradford-Hill criteria.
No RCT for Masks? No Problem
Other forms of evidence are available to judge effectiveness of this and other interventions
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