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[Preprint]. 2021 Oct 20:2021.10.20.21265137.
doi: 10.1101/2021.10.20.21265137.

Evidence of transmission from fully vaccinated individuals in a large outbreak of the SARS-CoV-2 Delta variant in Provincetown, Massachusetts

Katherine J Siddle, Lydia A Krasilnikova, Gage K Moreno, Stephen F Schaffner, Johanna Vostok, Nicholas A Fitzgerald, Jacob E Lemieux, Nikolaos Barkas, Christine Loreth, Ivan Specht, Christopher H Tomkins-Tinch, Jillian Silbert, Beau Schaeffer, Bradford P Taylor, Bryn Loftness, Hillary Johnson, Petra L Schubert, Hanna M Shephard, Matthew Doucette, Timelia Fink, Andrew S Lang, Stephanie Baez, John Beauchamp, Scott Hennigan, Erika Buzby, Stephanie Ash, Jessica Brown, Selina Clancy, Seana Cofsky, Luc Gagne, Joshua Hall, Rachel Harrington, Gabrielle L Gionet, Katherine C DeRuff, Megan E Vodzak, Gordon C Adams, Sabrina T Dobbins, Sarah D Slack, Steven K Reilly, Lisa M Anderson, Michelle C Cipicchio, Matthew T DeFelice, Jonna L Grimsby, Scott E Anderson, Brendan S Blumenstiel, James C Meldrim, Heather M Rooke, Gina Vicente, Natasha L Smith, Katelyn S Messer, Faye L Reagan, Zoe M Mandese, Matthew D Lee, Marianne C Ray, Marissa E Fisher, Maesha A Ulcena, Corey M Nolet, Sean E English, Katie L Larkin, Kyle Vernest, Sushma Chaluvadi, Deirdre Arvidson, Maurice Melchiono, Theresa Covell, Vaira Harik, Taylor Brock-Fisher, Molly Dunn, Amanda Kearns, William P Hanage, Clare Bernard, Anthony Philippakis, Niall J Lennon, Stacey B Gabriel, Glen R Gallagher, Sandra Smole, Lawrence C Madoff, Catherine M Brown, Daniel J Park, Bronwyn L MacInnis, Pardis C Sabeti

Evidence of transmission from fully vaccinated individuals in a large outbreak of the SARS-CoV-2 Delta variant in Provincetown, Massachusetts

Katherine J Siddle et al. medRxiv. .

Update in

  • Transmission from vaccinated individuals in a large SARS-CoV-2 Delta variant outbreak.
    Siddle KJ, Krasilnikova LA, Moreno GK, Schaffner SF, Vostok J, Fitzgerald NA, Lemieux JE, Barkas N, Loreth C, Specht I, Tomkins-Tinch CH, Paull JS, Schaeffer B, Taylor BP, Loftness B, Johnson H, Schubert PL, Shephard HM, Doucette M, Fink T, Lang AS, Baez S, Beauchamp J, Hennigan S, Buzby E, Ash S, Brown J, Clancy S, Cofsky S, Gagne L, Hall J, Harrington R, Gionet GL, DeRuff KC, Vodzak ME, Adams GC, Dobbins ST, Slack SD, Reilly SK, Anderson LM, Cipicchio MC, DeFelice MT, Grimsby JL, Anderson SE, Blumenstiel BS, Meldrim JC, Rooke HM, Vicente G, Smith NL, Messer KS, Reagan FL, Mandese ZM, Lee MD, Ray MC, Fisher ME, Ulcena MA, Nolet CM, English SE, Larkin KL, Vernest K, Chaluvadi S, Arvidson D, Melchiono M, Covell T, Harik V, Brock-Fisher T, Dunn M, Kearns A, Hanage WP, Bernard C, Philippakis A, Lennon NJ, Gabriel SB, Gallagher GR, Smole S, Madoff LC, Brown CM, Park DJ, MacInnis BL, Sabeti PC. Siddle KJ, et al. Cell. 2022 Feb 3;185(3):485-492.e10. doi: 10.1016/j.cell.2021.12.027. Epub 2021 Dec 23. Cell. 2022. PMID: 35051367 Free PMC article.

Abstract

Multiple summer events, including large indoor gatherings, in Provincetown, Massachusetts (MA), in July 2021 contributed to an outbreak of over one thousand COVID-19 cases among residents and visitors. Most cases were fully vaccinated, many of whom were also symptomatic, prompting a comprehensive public health response, motivating changes to national masking recommendations, and raising questions about infection and transmission among vaccinated individuals. To characterize the outbreak and the viral population underlying it, we combined genomic and epidemiological data from 467 individuals, including 40% of known outbreak-associated cases. The Delta variant accounted for 99% of sequenced outbreak-associated cases. Phylogenetic analysis suggests over 40 sources of Delta in the dataset, with one responsible for a single cluster containing 83% of outbreak-associated genomes. This cluster was likely not the result of extensive spread at a single site, but rather transmission from a common source across multiple settings over a short time. Genomic and epidemiological data combined provide strong support for 25 transmission events from, including many between, fully vaccinated individuals; genomic data alone provides evidence for an additional 64. Together, genomic epidemiology provides a high-resolution picture of the Provincetown outbreak, revealing multiple cases of transmission of Delta from fully vaccinated individuals. However, despite its magnitude, the outbreak was restricted in its onward impact in MA and the US, likely due to high vaccination rates and a robust public health response.

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