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


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

In This Article


Initial Outbreak and Public Health Response

The town of Provincetown, at the northern tip of Cape Cod in Massachusetts, has a population of ≈3,000 permanent residents and, during peak summer months, can reportedly reach a population size of up to 60,000 persons. During July 3–17, thousands of visitors from across the United States traveled to Provincetown and participated in large, densely packed indoor and outdoor gatherings marketed to adult male participants. Multiple continuous events were held at venues such as restaurants, bars, and guest houses. Local advisories at the time did not recommend mask wearing for fully vaccinated persons, and venues did not require participants to wear masks indoors.

By July 10, MA DPH received multiple reports of an increasing cluster of COVID-19 cases among Massachusetts residents who resided in or recently visited Provincetown, including cases among fully vaccinated persons. On July 14, Massachusetts state and local health officials responded to the increase in cases by expanding access to SARS-CoV-2 mobile testing and recommending testing for all persons who traveled to Provincetown since July 1 or had close contact with persons who showed positive test results for SARS-CoV-2, regardless of vaccination status. On July 15 and July 21, MA DPH issued Epidemic Information Exchange notifications to identify additional cases among residents of US public health jurisdictions outside Massachusetts.

Case Definitions

For this investigation, a primary cluster-associated 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 detection of SARS-CoV-2 RNA or antigen in a respiratory specimen from a person without history of travel to or residence in Provincetown during July 3–August 10 that was collected ≤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. The infectious period of a person who had a primary case was defined as 2 days before through 10 days after symptom onset or, if asymptomatic, 2 days before through 10 days after a positive test result. Persons were considered symptomatic if they reported any COVID-19-like symptom within 14 days before or after specimen collection.[17]

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 [] or Moderna [], or 1 dose of Johnson & Johnson []) and who had documentation in their state immunization information system or self-report of vaccination details (including vaccine product and dates of receipt) during case investigation. Non–fully vaccinated persons were those who were partially vaccinated or unvaccinated or whose vaccination status was unknown. Partially vaccinated persons were those who had received only 1 dose of a 2-dose vaccine series or were <14 days after vaccine completion at the time of specimen collection; unvaccinated persons and persons with unknown status were those without documentation or self-attestation of vaccination. A COVID-19 vaccine breakthrough case was a cluster-associated case in a person who was fully vaccinated before collection of a SARS-CoV-2 positive specimen.

Data Collection and Analysis

For this investigation, state and local public health departments identified primary cases by using travel history documented in their COVID-19 surveillance systems (capturing demographic data, previous COVID-19 illness, underlying medical conditions, vaccination history, symptoms, and clinical outcomes), as well as supplemental case investigation and contact tracing of persons who self-reported an association with the outbreak. Secondary cases were identified, to the extent feasible, through case investigation and contact tracing of primary cases. Self-reported underlying medical conditions associated with increased risk for severe COVID-19 included in this investigation were active cancer undergoing current treatment, autoimmune disease, cardiovascular disease, chronic kidney disease, chronic liver disease, chronic lung disease, current pregnancy, diabetes, solid organ or stem cell transplant, infection with HIV, and other immunocompromising conditions.[18]

Case data collected by state and local health departments were sent to MA DPH; personally identifiable information was removed before sharing with CDC. We performed data collation and analysis by using SAS software version 9.4 ( This activity was reviewed by CDC and was conducted consistent with applicable federal law and CDC policy.

Laboratory Testing

State/local public health laboratories and laboratory partners confirmed cases by using SARS-CoV-2 nucleic acid amplification test or antigen test. Laboratories used a variety of platforms to conduct testing and sequencing of available cluster-associated specimens; variant identification results were shared with MA DPH and subsequently with CDC. Sequences were uploaded to the GISAID database[19] or GenBank.[20]