Viral Dynamics of SARS-CoV-2 Variants in Vaccinated and Unvaccinated Persons
Open accessPublished version of a preprint
Abstract
Abstract Background The alpha and delta SARS-CoV-2 variants have been responsible for major recent waves of COVID-19 despite increasing vaccination rates. The reasons for the increased transmissibility of these variants and for the reduced transmissibility of vaccine breakthrough infections are unclear. Methods We quantified the course of viral proliferation and clearance for 173 individuals with acute SARS-CoV-2 infections using longitudinal quantitative RT-PCR tests conducted using anterior nares/oropharyngeal samples ( n = 199,941) as part of the National Basketball Association’s (NBA) occupational health program between November 28 th , 2020, and August 11 th , 2021. We measured the duration of viral proliferation and clearance and the peak viral concentration separately for individuals infected with alpha, delta, and non-variants of interest/variants of concern (non-VOI/VOC), and for vaccinated and unvaccinated individuals. Results The mean viral trajectories of alpha and delta infections resembled those of non-VOI/VOC infections. Vaccine breakthrough infections exhibited similar proliferation dynamics as infections in unvaccinated individuals (mean peak Ct: 20.5, 95% credible interval [19.0, 21.0] vs . 20.7 [19.8, 20.2], and mean proliferation time 3.2 days [2.5, 4.0] vs . 3.5 days [3.0, 4.0]); however, vaccinated individuals exhibited faster clearance (mean clearance time: 5.5 days [4.6, 6.6] vs . 7.5 days [6.8, 8.2]). Conclusions Alpha, delta, and non-VOI/VOC infections feature similar viral trajectories. Acute infections in vaccinated and unvaccinated people feature similar proliferation and peak Ct, but vaccinated individuals cleared the infection more quickly. Viral concentrations do not fully explain the differences in infectiousness between SARS-CoV-2 variants, and mitigation measures are needed to limit transmission from vaccinated individuals.
The claims and statistics of this paper haven’t been checked yet.
Run the check — free, no account needed. It reads the open-access text and checks the sources it cites.
Integrity signals
Registry
Cites
Statistics
Claims the paper makes
The claims and statistics of this paper haven’t been checked yet.
Run the check — free, no account needed. It reads the open-access text and checks the sources it cites.
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
The majority of COVID-19 vaccines evoke humoral and cellular immune responses against the SARS-CoV-2 spike protein; these responses may not prevent infection but robustly protect against severe COVID-19 for certain periods of time.
“The majority of COVID-19 vaccines are designed to evoke humoral and cellular immune responses against the SARS-CoV-2 spike protein — responses that may not prevent infection but robustly protect against severe COVID-19, at least for certain periods of time11,150–157.”
From COVID-19 and cellular senescence (2023) · cites this paper as [157]
Self-check
Percentages, sums and reported differences re-computed from the paper’s own numbers.
The self-check needs the paper’s full text.
The citation lists haven’t been fetched yet
References 29 · Cited by 335
- Authors
- Kissler, S. M., Fauver, J. R., Mack, C., Tai, C. G., Breban, M. I., Watkins, A. E., Samant, R. M., Anderson, D. J., Metti, J., Khullar, G., Baits, R., MacKay, M., Salgado, D., Baker, T., Dudley, J. T., Mason, C. E., Ho, D. D., Grubaugh, N. D., & Grad, Y. H.
- Affiliations
- Harvard University (US)
- Yale University (US)
- IQVIA (United States) (US)
- Duke University (US)
- Tempus Labs (United States) (US)
- Columbia University (US)
- Corresponding author
- Grad, Yonatan H.
- Venue
- New England Journal of Medicine
- Publisher
- Massachusetts Medical Society
- Published
- 2021-12-23
- Volume
- 385
- Issue
- 26
- Pages
- 2489-2491
- ISSN
- 0028-4793 (ISSN-L)
- 1533-4406
- PMC
- PMC8693673
- OpenAlex
- W3216106237
- Cited by
- 335
- References
- 29
- Citations by year
- 2026: 14 · 2025: 25 · 2024: 36 · 2023: 78 · 2022: 131 · 2021: 51
- FWCI
- 23.44
- Type
- journal article
- Language
- en
- Open access
- green
- doi.org
- Licence
- Locations
- New England Journal of Medicine (publishedVersion)
- medRxiv (acceptedVersion, cc-by-nc-nd)
- PubMed Central (publishedVersion)
- PubMed (publishedVersion)
- Funders
- National Basketball Association, and the National Basketball Players Association
- Huffman Family Donor Advised Fund
- Emergent Ventures at the Mercatus Center
- Morris-Singer Fund
- Topics
- Health Sciences › Medicine › Infectious Diseases › SARS-CoV-2 and COVID-19 Research
- Health Sciences › Medicine › Infectious Diseases › COVID-19 Clinical Research Studies
- Physical Sciences › Mathematics › Modeling and Simulation › COVID-19 epidemiological studies
- Keywords
- SARS-CoV-2, SARS-CoV-2 variants, viral dynamics, vaccination, breakthrough infection, viral load, SARS-CoV-2 variants of concern
- MeSH terms
- COVID-19, SARS-CoV-2, COVID-19 Vaccines, Breakthrough Infections, Bayes Theorem, Humans, Vaccination, Viral Load
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
Statistics and arithmetic are recomputed, not judged.
Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.
What counts as a claim ›How we measure confidence ›How we check this ›
Are you an author, or do you see a problem with this page? Request a review
