Multistate Outbreak of SARS-CoV-2 Infections, Including Vaccine Breakthrough Infections, Associated With Large Public Gatherings, United States

Radhika Gharpure; Samira Sami; Johanna Vostok; Hillary Johnson; Noemi Hall; Anne Foreman; Rebecca T. Sabo; Petra L. Schubert; Hanna Shephard; Vance R. Brown; Ben Brumfield; Jessica N. Ricaldi; Andrew B. Conley; Lindsay Zielinski; Lenka Malec; Alexandra P. Newman; Michelle Chang; Lauren E. Finn; Cameron Stainken; Anil T. Mangla; Patrick Eteme; Morgan Wieck; Alison Green; Alexandra Edmundson; Diana Reichbind; Vernell Brown Jr.; Laura Quiñones; Allison Longenberger; Elke Hess; Megan Gumke; Alicia Manion; Hannah Thomas; Carla A. Barrios; Adrianna Koczwara; Thelonious W. Williams; Marcia Pearlowitz; Moussokoura Assoumou; Alessandra F. Senisse Pajares; Hope Dishman; Cody Schardin; Xiong Wang; Kendalyn Stephens; Nakema S. Moss; Gurpalik Singh; Christine Feaster; Lindsey Martin Webb; Anna Krueger; Kristen Dickerson; Courtney Dewart; Bree Barbeau; Amelia Salmanson; Lawrence C. Madoff; Julie M. Villanueva; Catherine M. Brown; A. Scott Laney

Disclosures

Emerging Infectious Diseases. 2022;28(1):35-43. 

In This Article

Results

Description of the Outbreak

During July 5–31, 2021, a total of 1,098 persons who traveled to or resided in Provincetown during July 3–17 showed positive test results for SARS-CoV-2 (Figure 1). Of these, 625 (57%) were Massachusetts residents and 473 (43%) were visitors from 20 US states, predominantly New York (123, 26%) and California (87, 18%), as well as the District of Columbia (52, 11%) (Appendix Figure 1, https://wwwnc.cdc.gov/EID/article/28/1/21-2220-App1.pdf). Most primary cluster-associated cases were in men (88%), adults 19–49 years of age (66%), and non-Hispanic White persons (66%). Genomic sequencing of primary case specimens identified the B.1.617.2 (Delta) variant of SARS-CoV-2 in 364 (98%) of 371 sequenced specimens, the AY.3 sublineage (Delta) in 1 (0.3%), the AY.4 sublineage (Delta) in 3 (0.8%), and P.1 (Gamma) in 3 (0.8%).

Figure 1.

Primary clusterassociated cases of severe acute respiratory syndrome coronavirus 2 infection (n = 1,098), by vaccination status and date of specimen collection, after large public gatherings in Provincetown, Massachusetts, USA, July 2021. Fully vaccinated persons were those who were ≥14 days after completion of all recommended doses of a US Food and Drug Administration–authorized coronavirus disease vaccine (2 doses of Pfizer/BioNTech [https://www.pfizer.com] or Moderna [https://www.modernatx.com], or 1 dose of Johnson & Johnson [https://www.jandj.com]), with documentation in their state immunization information system or self-report of vaccination details during case investigation. Non–fully vaccinated includes persons who were partially vaccinated or unvaccinated or whose vaccination status was unknown.

Secondary Transmission

We identified 30 secondary cases of SARS-CoV-2 infection in residents from 7 states; date of SARS-CoV-2–positive specimen collection ranged from July 11 through July 29, 2021, resulting in 1,128 cluster-associated cases (Table 1, https://wwwnc.cdc.gov/EID/article/28/1/21-2220-T1.htm). Persons with secondary cases were epidemiologically linked to 26 persons who had primary cases (Figure 2). Eighteen (60%) of 30 secondary cases occurred in fully vaccinated persons, as did 21 (81%) of 26 primary cases; there were 16 primary/secondary case pairs in which both persons were fully vaccinated. Most persons who had secondary cases (21, 70%) were household contacts of persons who had primary cases.

Figure 2.

Transmission diagram of primary (n = 26) and secondary (n = 30) cluster-associated cases of severe acute respiratory syndrome coronavirus 2 (SARSCoV-2) infection, by vaccination status and date of symptom onset or specimen collection, after large public gatherings in Provincetown, Massachusetts, USA, July 2021. A primary case was defined as detection of SARS-CoV-2 RNA or antigen in a respiratory specimen collected from a person ≤14 days after travel to or residence in Provincetown during July 3–17. A secondary case was defined as detection of SARS-CoV-2 RNA or antigen in a respiratory specimen collected from a person ≤14 days after close contact (within 6 feet for a cumulative total of ≥15 minutes within a 24-hour period) with a person who had a primary case during their infectious period, and without history of travel to or residence in Provincetown during July 3–August 10. The infectious period of a person with a primary case was defined as 2 days before through 10 days after symptom onset or, if asymptomatic, 2 days before or through 10 days after a positive test result. A vaccine breakthrough case was a cluster-associated case in a person who completed all recommended doses of a US Food and Drug Administration–authorized COVID-19 vaccine (2 doses of Pfizer/BioNTech [https://www.pfizer.com] or Moderna [https://www.modernatx.com], or 1 dose of Johnson & Johnson [https://www.jandj.com]) ≥14 days before collection of a SARS-CoV-2–positive specimen. Gray shading indicates the event exposure period (July 3–17, 2021) in the primary case definition. Only primary cases associated with a secondary case are shown. Symptom onset of persons with secondary cases before symptom onset of persons with primary cases was observed in 4 pairs, co nsistent with previous reports (21,22), and could be caused by presymptomatic transmission (23,24) or variability in self-reported symptom onset date. Household contacts were exposed to persons who had a primary case within household settings. Settings of nonhousehold exposures were workplace (1), summer camp (2), social gatherings (4), shared ride (1), and unknown (1).

The age distribution of persons with primary and secondary cases differed (Table 2, https://wwwnc.cdc.gov/EID/article/28/1/21-2220-T2.htm); 5 children <12 years of age and 1 person ≥75 years of age had secondary cases. Equal proportions of persons with primary and secondary cases had symptomatic illness (96%). For 20 primary/secondary case pairs with reported symptom onset, the median time from primary to secondary symptom onset (serial interval) was 2 (range −1 to 13) days. Phylogenetic analyses of 3 available primary/secondary case pairs indicated that each case pair was genetically similar (Appendix Figure 2).

Characteristics of Vaccine Breakthrough and Non-breakthrough Cases

Among the 1,128 cluster-associated primary and secondary cases, we identified 918 (81%) vaccine breakthrough cases. We confirmed vaccination status by matching to the state immunization information system for 664 (72%) cases and by self-report for 254 (28%) cases. Among fully vaccinated persons, most were men (90%), 19–49 years of age (66%), and non-Hispanic White (71%); a total of 13% had ≥1 underlying medical condition associated with increased risk for severe COVID-19 (Table 1). Among nonfully vaccinated persons, 39 (19%) persons were partially vaccinated and 171 (81%) were unvaccinated or had unknown vaccination status.

Of the 918 persons who had breakthrough infections, 504 (55%) received the Pfizer/BioNTech vaccine, 293 (32%) received the Moderna vaccine, and 121 (13%) received the Johnson & Johnson vaccine. Characteristics of vaccine breakthrough cases were similar across vaccine products (Appendix Table 1). The median time from completion of vaccination to SARS-CoV-2–positive specimen collection was 105 (range 15–326) days (Figure 3). For all cases, 12 (3%) of 383 persons who had available data had a previous COVID-19 diagnosis: 10/345 (3%) fully vaccinated and 2/38 (5%) non–fully vaccinated persons (Table 1).

Figure 3.

Time from completion of coronavirus disease (COVID-19) vaccination to date of specimen collection, by vaccine product, among fully vaccinated persons (n = 918) who had primary and secondary cluster-associated cases of severe acute respiratory syndrome coronavirus 2 infection after large public gatherings in Provincetown, Massachusetts, USA, July 2021. Fully vaccinated persons were those who were ≥14 days after completion of all recommended doses of a US Food and Drug Administration–authorized COVID-19 vaccine (2 doses of Pfizer/BioNTech [https://www.pfizer.com] or Moderna [https://www.modernatx.com], or 1 dose of Johnson & Johnson [https://www.jandj.com]), with documentation in their state immunization information system or self-report of vaccination details during case investigation. Minimum time from completion of vaccination to specimen collection for persons who had breakthrough infections was 14 days. Median time from completion of vaccination to SARS-CoV-2–positive specimen collection was 105 (range 15–326) days. Median times from completion to infection, by vaccine product, were 104 (range 15–326) days for persons who received the Pfizer-BioNTech vaccine, 104 (range 50–280) days for persons who received the Moderna vaccine, and 115 (range 23–225) days for persons who received the Johnson & Johnson/Janssen vaccine. Two persons were ≥270 days after vaccination at the time of specimen collection; 1 was vaccinated with Moderna 280 days before; and the other person with Pfizer-BioNTech 326 days before. Both persons were vaccinated through COVID-19 vaccine clinical trials.

Symptoms and Clinical Outcomes

For the 1,036 persons who had a cluster-associated case and who reported symptom data, 996 (96%) had a symptomatic illness with onset dates ranging from July 1 to July 31 (Table 1). A similar percentage of fully vaccinated (96%) and non–fully vaccinated (95%) persons reported symptomatic illness; cough was the most commonly reported symptom among both groups (72% in fully vaccinated, 57% in non–fully vaccinated). The number of symptoms reported was also similar across both groups; fully vaccinated persons reported a median of 5 symptoms during illness (range 1–13) and non–fully vaccinated persons reported 4 (range 1–12).

Eight persons were hospitalized and subsequently discharged, including 7 (0.7%) fully vaccinated persons (of whom 2 were admitted to the intensive care unit during hospitalization) and 1 (0.5%) non–fully vaccinated person. Of the hospitalized patients, 6 (75%) reported an underlying medical condition: 5 (71%) of 7 fully vaccinated persons and 1 (100%) of 1 non–fully vaccinated person. No deaths were reported.

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