Letter to the Editor: Additional Context Regarding December 21 Board of Health Presentation

January 4, 2021

Submitted by Bill Knox

I believe some of the information Dr. Kiessling presented in her slides at the December 21 Board of Health meeting is potentially somewhat misleading, and I would like to provide what I believe is some useful additional context.

In her first finding, from the study at Mass General Brigham published in the August 12 2020 JAMA (https://jamanetwork.com/journals/jama/fullarticle/2768533), she presents an inaccurate picture of the results. The 3 percentage point drop she describes in positivity rates between 14.7% and 11.5% represents an overall 22% decrease, which would in itself be more significant than she suggests. But these numbers aren’t even the proper ones to cite. Those numbers are both for positivity rates that occurred after the introduction of masking of first workers and later patients – prior to those interventions, infection rates among tested staff had reached 21.3% and were increasing exponentially. The actual decrease in positivity rates was therefore even greater – 21.3% to 11.5%, a 46% percent decrease. This in a time frame (March 1 to April 30) when, as the authors note, cases were increasing significantly in the general public in Massachusetts. In a press release (https://www.brighamandwomens.org/about-bwh/newsroom/press-releases-detail?id=3608) on the study from Brigham and Women’s Hospital quoting one of the authors: “While we studied health care workers, the results also apply to other situations in which social distancing is not possible. For those who have been waiting for data before adopting the practice, this paper makes it clear: Masks work.”

Regarding the evidence for six feet (i.e., 2 meters) versus three feet of separation being sufficient physical distancing, Dr. Keissling stated that she could find no source for the “6-foot rule” distance and no reference documenting additional risk associated with reducing to 3 feet. Finding references proved to be not that challenging. As described in an August 25 2020 article in the BMJ (https://www.bmj.com/content/370/bmj.m3223), the original 6-foot rule was developed in the 19th century based on studies of visible droplets during coughing and sneezing, prior to a proper understanding of the role of aerosols and similar non-visible particles. Aerosols, which have been implicated in the spread of SARS-CoV-2, travel much farther and last in the air much longer than large droplets, and present a risk at distances of many meters, per the same BMJ article. So, how much more dangerous is 3 feet than 6? The UK’s Scientific Advisory Group for Emergencies (SAGE), referencing a number of recent studies, estimates that the additional risk at 3 feet versus 6 feet ranges from 2 to 10 times greater, depending on ventilation, orientation of the people, and other factors (https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/892043/S0484_Transmission_of_SARS-CoV-2_and_Mitigating_Measures.pdf).

Finally, regarding the capability of children and adolescents being effective transmitters of SARS-CoV-2, Dr. Keissling’s assertion that children are not likely vectors for infection is at best partially supported by recent studies. One, in particular, published in the Emerging Infectious Diseases Journal from the CDC, titled “Contact Tracing during Coronavirus Disease Outbreak, South Korea, 2020” (https://wwwnc.cdc.gov/eid/article/26/10/20-1315_article), shows that while children 0-9 do appear to be less likely (5.3% versus 11.8% across all age groups) to spread COVID-19 to household contacts, adolescents 10-19 years of age are the most likely to transmit to their household contacts – 18.6%.

Having additional testing available would be a welcome addition to the overall range of capabilities that are in use to combat COVID-19. But to present that message in a context that masks are by and large useless, that social distancing isn’t supported by research and can be reduced, and that children don’t have the potential to spread this virus is inconsistent with the available data.

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January 5, 2021 11:57 am

Thank you to Bill Knox for the information he has provided. It really makes obvious the need to wear a mask, however inconvenient this seems to many people.

James Bergin
January 4, 2021 9:16 pm

I appreciate the very thorough and careful work you have put into this letter. Your specificity enables a meaningful discussion of this critical issue.

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