Cryptic Transmission of the Delta Variant AY.3 Sublineage of SARS-CoV-2 among Fully Vaccinated Patients on an Inpatient Ward
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Abstract
Background
Recent reports indicate that vaccination is effective in reducing symptomatic infection with the Delta variant of SARS-CoV-2 (DV) but is less protective against asymptomatic transmission of DV in outpatients than for earlier variants.
Here we report cryptic transmission associated with high DV viral load among vaccinated patients on an inpatient medical-surgical ward.
Methods
This observational study included all persons diagnosed with breakthrough SARS-CoV-2 infections at the VA Boston Healthcare System (VABHS) from March 11, 2021 to July 31, 2021, including those tested for surveillance, admission, symptoms, and as part of an outbreak investigation in July 2021. SARS-CoV-2 infection was diagnosed by reverse-transcription polymerase chain reaction (PCR) (Cepheid). Variants were identified by MassARRAY SARS-CoV-2 Variant Panel (36-plex PCR, Agena BioScience) for most breakthrough cases after June 2021 Viral genomic sequencing was performed by the Jackson Laboratory.
Results
An inpatient was diagnosed with asymptomatic DV infection on routine pre-discharge testing. Contact tracing detected infection in 6 of 38 patients (15.8%), 1 of 168 staff (0.6%), and 1 of 6 visitors (16.7%). Infection at the time of diagnosis was asymptomatic in 4 proximate, vaccinated patients, 1 vaccinated visitor, and 1 vaccinated employee caring for 1 undiagnosed, infected, vaccinated patient. Patients were unmasked, whereas staff wore surgical masks. PCR cycle threshold (Ct) for breakthrough infections indicated more than 1000-fold higher viral load for DV (Ct:21.7±4.3; n=15) than for earlier variants (Ct: 31.8±10.9, n=12; p=.003 ( t -test)).
Conclusion
These findings demonstrate transmission of DV with high viral load between vaccinated inpatients, the continued efficacy of masking and vaccination for protecting healthcare personnel, and the potential need for post-admission surveillance to prevent cryptic DV transmission.
Article activity feed
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SciScore for 10.1101/2021.08.05.21261562: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Ethics IRB: The VABHS Institutional Review Board determined that this was a quality improvement project and exempted this study from review. Sex as a biological variable not detected. Randomization not detected. Blinding not detected. Power Analysis not detected. Table 2: Resources
No key resources detected.
Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:This observational study has several limitations. The outbreak included a small number of individuals. The absence of full viral genome …
SciScore for 10.1101/2021.08.05.21261562: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Ethics IRB: The VABHS Institutional Review Board determined that this was a quality improvement project and exempted this study from review. Sex as a biological variable not detected. Randomization not detected. Blinding not detected. Power Analysis not detected. Table 2: Resources
No key resources detected.
Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:This observational study has several limitations. The outbreak included a small number of individuals. The absence of full viral genome sequencing on all 8 cases prevented clear identification of the source and trajectory of viral transmission. One case was not typed to positively identify the Delta variant. Finally, though the data demonstrate that asymptomatic infection and transmission of the Delta variant may occur in vaccinated persons, this study does not address the relative risk for Delta variant infection in vaccinated versus unvaccinated persons.
Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We did not find any issues relating to the usage of bar graphs.
Results from JetFighter: We did not find any issues relating to colormaps.
Results from rtransparent:- Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
- Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
- No protocol registration statement was detected.
Results from scite Reference Check: We found no unreliable references.
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