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Review 1: "Transmission Potential of Vaccinated and Unvaccinated Persons Infected with the SARS-CoV-2 Delta Variant in a Federal Prison, July-August 2021"

Published onJul 27, 2022
Review 1: "Transmission Potential of Vaccinated and Unvaccinated Persons Infected with the SARS-CoV-2 Delta Variant in a Federal Prison, July-August 2021"
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key-enterThis Pub is a Review of
Transmission potential of vaccinated and unvaccinated persons infected with the SARS-CoV-2 Delta variant in a federal prison, July—August 2021

AbstractBackgroundThe extent to which vaccinated persons who become infected with SARS-CoV-2 contribute to transmission is unclear. During a SARS-CoV-2 Delta variant outbreak among incarcerated persons with high vaccination rates in a federal prison, we assessed markers of viral shedding in vaccinated and unvaccinated persons.MethodsConsenting incarcerated persons with confirmed SARS-CoV-2 infection provided mid-turbinate nasal specimens daily for 10 consecutive days and reported symptom data via questionnaire. Real-time reverse transcription-polymerase chain reaction (RT-PCR), viral whole genome sequencing, and viral culture was performed on these nasal specimens. Duration of RT-PCR positivity and viral culture positivity was assessed using survival analysis.ResultsA total of 978 specimens were provided by 95 participants, of whom 78 (82%) were fully vaccinated and 17 (18%) were not fully vaccinated. No significant differences were detected in duration of RT-PCR positivity among fully vaccinated participants (median: 13 days) versus those not fully vaccinated (median: 13 days; p=0.50), or in duration of culture positivity (medians: 5 days and 5 days; p=0.29). Among fully vaccinated participants, overall duration of culture positivity was shorter among Moderna vaccine recipients versus Pfizer (p=0.048) or Janssen (p=0.003) vaccine recipients.ConclusionsAs this field continues to develop, clinicians and public health practitioners should consider vaccinated persons who become infected with SARS-CoV-2 to be no less infectious than unvaccinated persons. These findings are critically important, especially in congregate settings where viral transmission can lead to large outbreaks.

RR:C19 Evidence Scale rating by reviewer:

  • Reliable. The main study claims are generally justified by its methods and data. The results and conclusions are likely to be similar to the hypothetical ideal study. There are some minor caveats or limitations, but they would/do not change the major claims of the study. The study provides sufficient strength of evidence on its own that its main claims should be considered actionable, with some room for future revision.



In this manuscript, Salvatore et al. examine the degree to which individuals vaccinated against the SARS-CoV-2 virus contribute to the spread of the COVID-19 Delta variant using a sample of highly vaccinated incarcerated individuals in a federal Texas prison. This question is important given that COVID-19 vaccines are not fully effective in preventing the transmission of the virus and that new variants will continue to develop as long as the pandemic continues. The presence of new variants, including the most recent Omicron variant, warrant continued investigation into not only the efficacy of COVID-19 vaccinations but also detailed understandings of the mechanisms by which transmission is exacerbated. Using nasal specimens collected from 95 incarcerated individuals (78 who were fully vaccinated and 17 who were not fully vaccinated) over a period of 10 days exposed to the COVID-19 Delta variant, the authors utilize survival analysis to determine the duration of RT-PCR and viral culture positivity, and RT-PCR Ct value (which indicates the level of viral nucleic acid in a sample). A total of 978 specimens for RT-PCR, with 51% of the specimens testing positive for the presence of the SARS-CoV-2 virus. A total of 842 samples provided a viral culture results, with 9% having a positive viral result. The findings are insightful, documenting no significant difference in neither RT-PCR positivity nor viral culture positivity between those fully vaccinated and those not fully vaccinated. Similarly, no difference was found regarding Ct values among samples tested positive via RT-PCR by vaccination status. Importantly, the authors do document that those who received the Moderna had shorter duration of viral culture positivity compared to those who received Pfizer or Janssen vaccines. Stratifying by time since COVID-19 vaccination and prior COVID-19 infection, the authors find no significant differences in duration of culture positivity. The implications of such findings are that those who are vaccinated against the SARS-CoV2 virus should be treated equally as infectious as those unvaccinated during the development of public health guidance around COVID-19 mitigation. The authors argue that within the context of congregate settings, particularly correctional facilities, this means that those exposed to the SARS-CoV-2 virus should quarantine regardless of vaccination status and testing should occur. This manuscript adequately documents its limitations, including small sample sizes that could lead to underpower analyses and self-reported COVID-19 symptom data. Uniquely, this manuscript contributes to the knowledge around viral shedding from vaccinated persons infected with the COVID-19 Delta variant using a longitudinal study design. Further, it utilizes a sample of individuals with high vaccination rates and who are particularly high risk for COVID-19 outbreaks Given the conditions of incarceration (i.e., close living arrangements, limited ability to social distance).


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