Supported by intramural funds (K23NS109284 [to Dr. Hefti]) from the National Institute of Neurological Disorders and Stroke. The reagent used in this study (Genomic RNA from SARS-CoV-2, Isolate USA-WA1/2020, NR-52285) was deposited by the Centers for Disease Control and Prevention and obtained through BEI Resources Repository of the National Institute of Allergy and Infectious Diseases of the National Institutes of Health.
Disclosure forms provided by the authors are available with the full text of this letter at NEJM.org.

The opinions expressed here are those of the authors and are not necessarily representative of those of the Uniformed Services University, the U.S. Department of Defense, or the U.S. Army, Navy, or Air Force or any other federal agency.
This letter was published on December 30, 2020, at NEJM.org.

Supplementary Appendix
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Disclosure Forms
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