Lisa A. Cosimi, MD Division of Infectious Diseases Brigham and Women’s Hospital Boston, Massachusetts

Study Evaluates Risk of Transmission with Negative Home Test after Covid Interview with:

Lisa A. Cosimi, MD Division of Infectious Diseases Brigham and Women’s Hospital Boston, Massachusetts

Dr. Cosimi

Lisa A. Cosimi, MD
Division of Infectious Diseases
Brigham and Women’s Hospital
Boston, Massachusetts  What is the background for this study? 

Response: Response: Current CDC COVID-19 isolation guidance allows for ending isolation after day 5 for non-immunocompromised individuals if they are afebrile and with improving symptoms, or if the individual is asymptomatic from the start. It has been proposed that rapid antigen tests (RATs) may assist in determining when individuals are no longer infectious. Specifically, a negative test would be potentially reassuring for an individual not being transmissible, while a positive test could be suggestive of continued infectiousness.  However, there is little data about use of RATs in this particular setting and how they may correlate with ongoing risk of transmission as they were developed to be used during the initial diagnosis of infection, not in the later phase.  What are the main findings?

Response:  In the manuscript, we present key findings from an observational cohort study of 40 individuals newly testing positive for SARS-CoV-2 who completed entry and daily symptom logs and self-tested with the Flowflex™ lateral flow RAT starting day 6 until negative. In addition to the daily rapid antigen testing, we collected anterior nasal and oral swabs on a subset of individuals for viral culture. Findings included:

  • 75% of individuals remained rapid antigen test positive on day 6. Many of these individuals reported resolved symptoms on the day the RAT remained positive (day 6-14).
  • We detected culturable virus in 35% of the subset who were sampled on day 6.
  • No individuals with a negative RAT were culture positive.
  • 50% of individuals with a positive RAT were also culture positive (ie potentially transmissible). 50% were negative
  • Of the 6 individuals who were culture positive on day 6, 4 would have been released per current guidance if they relied on symptoms alone, as they had improving symptoms or never reported symptoms. What should readers take away from your report? 

Response: The data suggest that a negative RAT result in individuals with residual symptoms could provide reassurance about ending isolation.  A recommendation to end isolation based solely on improving symptoms risks releasing individuals with potentially transmissible virus.  This underscores the CDC recommendation to wear a tight fitting mask and avoid high risk transmission areas to reduce the chance of onward transmission for 10 days after a diagnosis of SARS-CoV-2.  However, the data also suggest that a universal requirement to end isolation only if the RAT is negative may unduly extend isolation for individuals that actually aren’t likely to transmit virus. What recommendations do you have for future research as a result of this work?

Response: Additional data from larger cohorts including individuals who have received antiviral treatment, and in cases of symptom rebound would add to our understanding of viral dynamics and risk of transmission after infection with SARS-CoV-2.


Cosimi LA, Kelly C, Esposito S, et al. Duration of Symptoms and Association With Positive Home Rapid Antigen Test Results After Infection With SARS-CoV-2. JAMA Netw Open. 2022;5(8):e2225331. doi:10.1001/jamanetworkopen.2022.25331

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Last Updated on August 3, 2022 by Marie Benz MD FAAD