SGEM#309: That’s All Joe Asks of You – Wear a Mask

Date: November 25th, 2020 Guest Skeptic: Dr. Joe Vipond has worked as an emergency physician for twenty years, currently at the Rockyview General Hospital.  He is the President of the national charity Canadian Association of Physicians for the Environment (CAPE), as well as the co-founder and co-chair of the local non-profit the Calgary Climate Hub, and during COVID, the co-founder of Masks4Canada. Joe grew up in Calgary and continues to live there with his wife and two daughters. Reference: Bundgaard et al. Effectiveness of Adding a Mask Recommendation to Other Public Health Measures to Prevent SARS-CoV-2 Infection in Danish Mask Wearers: A Randomized Controlled Trial. Annals of Internal Medicine 2020 Case: : Alberta is the last province in Canada that has yet to enact a mandatory mask policy. Should they do it? Mask4All Debate Background: During a respiratory pandemic, there still remains substantial questions about the utility and risk of facial masks for prevention of viral transmission. We debated universal mandatory masking back in the spring on an SGEM Xtra episode. Some very well known evidence-based medicine experts like Dr. Trisha Greenhalgh were advocating in favour of stricter mask regulations based on the precautionary principle (Greenhalgh et al BMJ 2020). She was challenged on her position (Martin et al BMJ 2020) and responded with an article called: Laying straw men to rest (Greenhalgh JECP 2020). A limitation of science is the available evidence. SARS-CoV-2 is a novel virus and we did not have much information specifically about the efficacy of masks. We needed to extrapolate from previous research on masks and other respiratory illnesses. However, we do have a firm understanding of the germ theory of disease and masks have been used for over 100 years as an infectious disease strategy. It was surgeons in the late 1890’s that began wearing masks in the operating theaters. There was skepticism back then as to the efficacy of a “surgical costume” (bonnet and mouth covering) to prevent disease and illness during surgery (Strasser and Schlich Lancet 2020). There was one recent cluster randomized control trial  looking at surgical masks, cloth masks or a control group in healthcare workers (MacIntyre et al BMJ 2015). The main outcomes were clinical respiratory illness, influenza-like illness and laboratory-confirmed respiratory virus infection. All infectious outcomes were highest in the cloth mask group, lower in the control group and lowest in the medical mask group. As with all studies this one had limitations. One of the main ones is this looked at healthcare workers wearing a mask as protection not in the general public as a source control. There has been a systematic review meta-analysis on physical distancing, face masks and eye protection to prevent SARS-Cov-2 (Chu et al Lancet 2020). With regards to masks, they found that face masks could result in a large reduction in risk of infection with a stronger association with N95 or similar respirators compared with disposable surgical masks or similar cloth masks. SRMA also have limitations and one of the main ones is they are dependent on the quality of the included studies. This review in the Lancet included ten studies (n=2,647) with seven from China, eight looking at healthcare workers (not general public) and only one looking at COVID19. All 10 studies were observational designs and the authors correctly only claim associations. They also say their level of certainty about masks being associated with a decrease in disease is considered “low certainty” based on the GRADE category of evidence. When considering an intervention, we cannot just consider the potential benefit, but we must also consider the potential harms. There is little or no evidence that wearing a face mask leads to potential harms. Yes, there are case reports of harm, children under 2 years of age should not wear face coverings (AAP News) and studies systematically under report adverse events (Hodkinson et al BMJ 2013) but the pre-test probability of individual harm is very low. What many studies on masks conclude is we need better evidence to inform our decisions. Now we have the first published randomized control trial on mask wearing in public to prevent transmission of COVID19. Clinical Question: Does recommending surgical mask use outside the home reduces wearers' risk for SARS-CoV-2 infection in a setting where masks were uncommon and not among recommended public health measures? Reference: Bundgaard et al. Effectiveness of Adding a Mask Recommendation to Other Public Health Measures to Prevent SARS-CoV-2 Infection in Danish Mask Wearers: A Randomized Controlled Trial. Annals of Internal Medicine 2020 Population: Danish adults > 18 years of age without symptoms associated with SARS-CoV-2 (or previously tested positive for SARS-CoV-2), working out-of-home with exposure to other people for more than three hours per day and who do not normally wear a face mask at work Exclusions: 18 years of age and younger, previously tested positive for SARS-CoV-2 or wears a face mask at work Intervention: Participants were encouraged to follow the authorities general COVID-19 precautions and to wear a surgical face mask for a 30-day period when out-of-home (50 surgical masks were provided) Comparison: Participants were encouraged to follow the authorities general COVID-19 precautions and no face masks were provided and no face mask recommendation Outcome: Primary Outcome: SARS-CoV-2 infection at one month by either antibody testing (IgG and/or IgM), polymerase chain reaction (PCR), or hospital diagnosis. Secondary Outcome: PCR positivity for other respiratory viruses Tertiary Outcomes: Returned swabs, Psychological aspects of face mask wearing in the community, Cost-effectiveness analyses on the use of surgical face masks, Preference for self-conducted home swab vs. healthcare conducted swab at hospital or similar, Symptoms of COVID-19, Self-assessed compliance with health authority guideline on hygiene, Willingness to wear face masks in the future, Health care diagnosed COVID-19 or SARS-CoV-2 (antibodies and/or PCR), mortality as with COVID-19 and all-cause mortality, Presence of bacteria; Mycoplasma pneumonia, Haemophilia influenza and Legionella pneumophila (to be obtained from registries when made available), Frequency of infected house-hold members between the two groups, Frequency of sick-leave between the two groups (to be obtained from registries when made available), and Predictors of primary outcome or its components Authors’ Conclusions: “The recommendation to wear surgical masks to supplement other public health measures did not reduce the SARS-CoV-2 infection rate among wearers by more than 50% in a community with modest infection rates, some degree of social distancing, and uncommon general mask use. The data were compatible with lesser degrees of self-protection.” Quality Checklist for Randomized Clinical Trials: The study population included or focused on those in the emergency department. No The patients were adequately randomized. Yes The randomization process was concealed. Yes The patients were analyzed in the groups to which they were randomized. Yes The study patients were recruited consecutively (i.e. no selection bias). No The patients in both groups were similar with respect to prognostic factors. Yes All participants (patients, clinicians, outcome assessors) were unaware of group allocation. No All groups were treated equally except for the intervention. Yes Follow-up was complete (i.e. at least 80% for both groups). Yes All patient-important outcomes were considered. Unsure The treatment effect was large enough and precise enough to be clinically significant. Unsure Key Results: The trial included 6,024 people with mean age of 47 years and almost 2/3 identified as female. No statistical difference in SARS-CoV-2 infection between the mask group and no mask group Primary Outcome: SARS-Cov-2 infection (Intension-to-Treat) 1.8% mask group vs. 2.1% no mask group − 0.3 percentage point (95% CI, −1.2 to 0.4) P= 0.38 Odds Ratio (OR) 0.82 (95% CI, 0.54 to 1.23) P= 0.33 Per-Protocol Analysis: 1.8% mask group vs. 2.1% no mask group with absolute difference -0.4% (95% CI -1.2 to 0.5) P = 0.40 and OR 0.84 (95% CI, 0.55 to 1.26) P = 0.40 Secondary Outcomes: Other viral infection 0.5% mask group vs. 0.6% no mask group There are a number of nerdy points we could have discussed but in typical fashion and to keep the blog/podcast to a digestible length we have highlighted five. 1) Methods: Some questions have been raised about the methodology. This trial was registered with ClinicalTrials.gov (NCT04337541). The trial protocol was registered with the Danish Data Protection Agency (P-2020-311), adhered to the recommendations for trials described in the SPIRIT Checklist and they published their methodology in the Danish Medical Journal (Bundgaard et al 2020). Some of the comments about the methodology specifically referenced the lack of ethics approval. However, the researchers presented the protocol to the independent regional scientific ethics committee of the Capital Region of Denmark, which did not require ethics approval in accordance with Danish legislation. The trial was also done in accordance with the principles of the Declaration of Helsinki. In the supplemental material there is a letter from the Chairman of the Ethics Committee saying they do not require ethics approval. It is hard to be critical of the researchers who took reasonable steps to address ethical concerns and were told they did not need ethics approval.