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We used daily real-time reverse-transcription polymerase chain reaction (RT-PCR) results from 67 cases of SARS-CoV-2 infection in a household transmission study, conducted April 2020-May 2021, to examine the trajectory of cycle threshold (Ct) values, an inverse correlate of viral RNA concentration. Ct values varied across RT-PCR platforms and by participant age. Specimens collected from children and adolescents had higher Ct values and adults aged ≥50 years showed lower Ct values than adults aged 18-49 years. Ct values were lower on days when participants reported experiencing symptoms, with the lowest Ct value occurring 2-6 days after symptom onset., Competing Interests: Potential conflicts of interest. C. G. G. reports grants from Campbell Alliance/Syneos, the National Institutes of Health, the Food and Drug Administration, the Agency for Health Care Research and Quality, and Sanofi-Pasteur; and consultation fees from Pfizer, Merck, and Sanofi-Pasteur. N. B. H. reports grant support from Sanofi-Pasteur and Quidel. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed., (Published by Oxford University Press on behalf of Infectious Diseases Society of America 2022.)

Purpose: Vaccine‐associated enhanced disease (VAED) is a theoretical concern with new vaccines, although trials of authorized vaccines against SARS‐CoV‐2 have not identified markers for VAED. The purpose of this study was to detect any signals for VAED among adults vaccinated against coronavirus disease 2019 (COVID‐19). Methods: In this cross‐sectional study, we assessed COVID‐19 severity as a proxy for VAED among 400 adults hospitalized for COVID‐19 from March through October 2021 at eight US healthcare systems. Primary outcomes were admission to an intensive care unit (ICU) and severe illness (score ≥6 on the World Health Organization [WHO] Clinical Progression Scale). We compared the risk of outcomes among those who had completed a COVID‐19 vaccine primary series versus those who were unvaccinated. We incorporated inverse propensity weights for vaccination status in a doubly robust regression model to estimate the causal average treatment effect. Results: The causal risk ratio in vaccinated versus unvaccinated was 0.36 (95% confidence interval [CI], 0.15–0.94) for ICU admission and 0.46 (95% CI, 0.25–0.76) for severe illness. Conclusion: Among hospitalized patients, reduced disease severity in those vaccinated against COVID‐19 supports the absence of VAED. [ABSTRACT FROM AUTHOR]

The article explores the implications of a shortened quarantine among households on the spread of COVID-19 in the U.S. The Centers for Disease Control and Prevention (CDC) has recommended two options to reduce the duration of quarantine for close contacts without symptoms. The use of reverse transcription-polymerase chain reaction (RT-PCR) to detect COVID-19 is also discussed.