COVID-19: Household Transmission / Regeneron Trial Stopped / Mask Safety Confirmed

By Kelly Young

Edited by Susan Sadoughi, MD, and André Sofair, MD, MPH

Here are some of the most recent developments in COVID-19:

Household transmission common: An MMWR study finds a secondary infection rate of 53% among household contacts of people with COVID-19. Researchers studied transmission in roughly 100 households in which someone had COVID-19 in Tennessee and Wisconsin from April through September. Household members completed symptom diaries and provided regular nasal and saliva samples for testing. Significant transmission occurred in households regardless of whether the index patient was an adult or child. Three quarters of the household members who tested positive for SARS-CoV-2 did so within 5 days of the index patient becoming sick. The authors write: "Because household transmission of SARS-CoV-2 is common and can occur rapidly after the index patient's illness onset, persons should self-isolate immediately at the onset of COVID-like symptoms, at the time of testing as a result of a high risk exposure, or at the time of a positive test result, whichever comes first. Concurrent to isolation, all members of the household should wear a mask when in shared spaces in the household."

Part of Regeneron trial stopped: An independent data monitoring committee has recommended that Regeneron stop enrolling additional COVID-19 patients who require high-flow oxygen or mechanical ventilation in the trial of its investigational REGN-COV2 antibody cocktail. The recommendation was based on "an unfavorable risk/benefit profile" in these groups. Trials have not stopped for hospitalized patients who require either no or low-flow oxygen or for outpatients.

Mask safety confirmed: A small study in JAMA confirms the safety of wearing nonmedical masks for members of the public. Roughly 25 seniors in Canada were given three-layer, disposable masks and asked to self-monitor their peripheral oxygen saturation levels (SpO2) before, during, and after wearing the mask while they were at rest or doing regular activities around the house. The pooled mean SpO2 levels were 96.1% prior to, 96.5% during, and 96.3% after wearing the mask. A difference of 3 percentage points or more is considered clinically meaningful. The authors conclude: "These results do not support claims that wearing nonmedical face masks in community settings is unsafe."