December 15, 2020 - a podcast by COVID19LST

In today's episode we discuss:

—Climate: What are the COVID-19 vaccine trial ethics once we have efficacious vaccines? An expert opinion penned by bioethicists from the National Institutes of Health and Fogarty International Center in Bethesda, MD explore the ethics of continuing blinded, placebo-controlled trials for COVID-19 vaccines in the wake of a safe and efficacious vaccine being approved for widespread use. Authors argue it is ethical to continue trials if participants consent and the risk-benefit profile of the trial remains acceptable, because continuing trials could lead to the discovery of longer lasting vaccines, better immunity, or greater efficacy in subpopulations. However, the authors emphasize trial participants in blinded, placebo-controlled trials should be informed of the availability of the vaccine and allowed to leave the trial if they desire.

—Understanding the Pathology: The L37F mutation may be critical to asymptomatic COVID-19 infection and transmission. Computer scientists from the University of Illinois analyzed 75,775 SARS-CoV-2 complete genome isolates to explore virological characteristics in asymptomatic COVID-19. They found patients with asymptomatic COVID-19 were significantly more likely to have the SARS-CoV-2 single nucleotide mutation 11083G>T-(L37F) on Non-Structural Protein 6 (NSP 6)(r=0.61, p=5.42×10^-56) and countries with the highest L37F mutation ratio had lower death ratio. Artificial intelligence (AI), topological data analysis (TDA), and network analysis revealed L37F destabilized NSP6's structure in a way that impeded viral assembly and replication. Authors suggest L37F mutation as a possible explanation for asymptomatic COVID-19 and encourage further research on therapies targeting NSP6.

—Transmission & Prevention: Transmissibility of COVID-19 depends on the viral load around onset in adult and symptomatic patients. Infectious disease specialists and microbiologists from the Toyama University Graduate School of Medicine and Pharmaceutical Sciences in Japan conducted a case-control study comparing patients with 14 COVID-19 who did ("index patients") and 14 who did not transmit SARS-CoV-2 to another patient. They found index patients showed higher viral loads at onset compared to non-index patients (6.6 [5.2 to 8.2] log copies/μL vs. 3.1 [1.5 to 4.8]) and that, in general, symptomatic patients had a higher initial viral load (2.8 log copies/μL) than asymptomatic patients (0.9 log copies/μL, p<0.01). Authors suggest elevated nasopharyngeal viral load contributes to secondary transmission of SARS-CoV-2, and that understanding the viral threshold for infectivity can better quarantine and isolation policies.

· Peripheral oxygen saturation does not decrease in older persons wearing nonmedical face masks in community settings. Internists from McMaster University in Canada conducted a crossover study of 25 retirement home residents older than 65 to monitor self-measured peripheral oxygen saturation (SpO2) with use of a three-layer disposable nonmedical face mask. They found pooled mean SpO2 was 96.1%, 96.5%, 96.3% in the hour prior to use, during one hour of use, and one hour after wearing the masks, respectively.Authors suggest despite some public concerns about mask safety, the use of nonmedical face masks is not associated with a decrease in SpO2 in older populations.

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