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Reduction of secondary transmission of SARS-CoV-2 in households by face mask use, disinfection and social distancing: a cohort study in Beijing, China
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  • Published on:
    Co-linearity between pre-symptomatic and post-symptomatic mask wearing
    • Shaun A Truelove, Epidemiologist, Assistant Scientist Johns Hopkins Bloomberg School of Public Health

    The effectiveness of masks in the household is a critically important topic for control of SARS-CoV-2 transmission. I am concerned the multivariate regression performed in this analysis incorrectly attributed all of the effect of post-symptomatic mask-wearing to the pre-symptomatic mask-wearing variable. It is highly likely that these 2 variables are highly co-linear, and looking at Table 2, it appears likely that those families that wore masks pre-symptoms (n=27 without transmission, n=4 with transmission) were largely the same families where all members of the household wore masks post-symptoms (n=31 without transmission, n=5 with transmission). It's likely there are not enough numbers to further disentangle whether pre-symptom or post-symptom mask-wearing truly was the benefit - most likely it's some of both.

    The message that post-symptomatic mask-wearing has no effect appears to lack sufficient support, so I would caution anyone jumping to use that conclusion here.

    Conflict of Interest:
    None declared.
  • Published on:
    Preventing viral transmissions in communities and households: strategies from a multidisciplinary view highly needed
    • Carla Peeters, Director: immunology, nutrition and health transformation expert COBALA Good Care Feels Better®
    • Other Contributors:
      • Mattias Desmet, Professor of Psychology and Educational Sciences

    Rapid response

    Preventing viral transmissions in communities and households: strategies from a multidisciplinary view highly needed

    Re: Reduction of secondary transmission of SARS-COV-2 in households by facemask use, disinfection and social distancing: a cohort study in Beijing, China. Yu Wang. BMJ Global Health 2020; 5: e002794, doi: 10.1136/bmjgh-2020-002794

    Dear Editor,

    In their original research in BMJ Global Health Wang et al. (1) claim that their study provides the first evidence for the effectiveness of face mask use and social distancing in preventing COVID-19 transmission, not just in public spaces but inside the household with members at risk of getting infected. They argue that these non-pharmaceutical interventions (NPI) reduce risk for families living with someone in quarantine or isolation and families of healthcare workers who may face ongoing risk and that NPI are effective at preventing transmission even in homes that are crowded and small.

    More specific, Wang et al. (1) conclude that face mask use 2 days prior to symptom onset could be preventing secondary transmission while starting to wear facemasks after the onset of symptoms did not have any effect on a secondary transmission. Almost a quarter of family members became infected in the families with a second transmission ( total of 77 persons with 13 children with a mean age of 3 years with mild symptoms and one child with asymptomatic symptoms, 64 adult cases; 3 as...

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    Conflict of Interest:
    None declared.