Investigation of SARS-CoV-2 Transmission Associated With a Large Indoor Convention — New York City, November–December 2021

During November 19–21, 2021, an indoor convention (event) in New York City (NYC), was attended by approximately 53,000 persons from 52 U.S. jurisdictions and 30 foreign countries. In-person registration for the event began on November 18, 2021. The venue was equipped with high efficiency particulate air (HEPA) filtration, and attendees were required to wear a mask indoors and have documented receipt of at least 1 dose of a COVID-19 vaccine.* On December 2, 2021, the Minnesota Department of Health reported the first case of community-acquired COVID-19 in the United States caused by the SARS-CoV-2 B.1.1.529 (Omicron) variant in a person who had attended the event (1). CDC collaborated with state and local health departments to assess event-associated COVID-19 cases and potential exposures among U.S.-based attendees using data from COVID-19 surveillance systems and an anonymous online attendee survey. Among 34,541 attendees with available contact information, surveillance data identified test results for 4,560, including 119 (2.6%) persons from 16 jurisdictions with positive SARS-CoV-2 test results. Most (4,041 [95.2%]), survey respondents reported always wearing a mask while indoors at the event. Compared with test-negative respondents, test-positive respondents were more likely to report attending bars, karaoke, or nightclubs, and eating or drinking indoors near others for at least 15 minutes. Among 4,560 attendees who received testing, evidence of widespread transmission during the event was not identified. Genomic sequencing of 20 specimens identified the SARS-CoV-2 B.1.617.2 (Delta) variant (AY.25 and AY.103 sublineages) in 15 (75%) cases, and the Omicron variant (BA.1 sublineage) in five (25%) cases. These findings reinforce the importance of implementing multiple, simultaneous prevention measures, such as ensuring up-to-date vaccination, mask use, physical distancing, and improved ventilation in limiting SARS-CoV-2 transmission, during large, indoor events.^†

An indoor convention in NYC with approximately 53,000 attendees was held during November 19–21, 2021. The facility was equipped with HEPA filters, and attendees were required to have documented receipt of at least 1 dose of COVID-19 vaccine and to use face masks while indoors. On December 2, 2021, the Minnesota Department of Health identified a case of COVID-19 caused by the Omicron variant in an attendee. State and local health departments collaborated with CDC to determine the extent of transmission during the convention and to make public health recommendations.

Two primary data sources were used in this investigation. The first was a list of attendees residing within the jurisdictions of participating state and local health departments. These attendees were matched with data from COVID-19 surveillance systems using personal identifiers (name and complete or partial address). Health departments identified positive and negative SARS-CoV-2 test results, demographic data, and vaccination histories^§ for attendees. An event-associated case was defined as SARS-CoV-2 infection confirmed by reverse transcription–polymerase chain reaction or antigen testing in an event attendee during November 18–December 5, 2021. Sequencing of available specimens was conducted by state public health laboratories using multiple platforms^¶; variant identification results were shared with CDC.

The second data source, an online anonymous survey, was administered via text message (29,766 text messages sent) and email (28,893 emails delivered) to approximately 35,000 attendees from 52 jurisdictions with available contact information, during December 11–19, 2021. Respondents were asked to report SARS-CoV-2 testing history and results, COVID-19 vaccination status, symptom history,** and exposure data during the event, and close contacts during and after the event. Available surveillance information and survey responses from U.S. resident attendees who received positive and negative test results were compared. Wilcoxon rank-sum tests were used for continuous data, and Pearson’s chi-square or Fisher’s exact tests were used for categorical data; statistical significance was defined as p<0.05.^†† This activity was reviewed by CDC and was conducted consistent with applicable federal law and CDC policy.^§§

Using COVID-19 surveillance systems, 48 public health jurisdictions reviewed data for 34,072 registered attendees; 39 jurisdictions reported a positive or negative result for 4,560 (13.4%) attendees, including 13 (<1%) self-tests^¶¶ (from two states) (Table 1). Among 3,845 (84.3%) attendees with test and vaccination data, 3,248 (84.5%) had received a primary vaccination series, an additional 467 (12.1%) had received a booster dose,*** and 130 (3.4%) were partially vaccinated.

Among the 4,560 attendees with test result data, 119 (2.6%) event-associated cases were identified by January 6, 2022, from 16 jurisdictions (Figure). Among event-associated cases the median age was 26.5 years (IQR = 23.0–36.6 years), 65 (54.6%) were New York residents, and among 116 with gender data available, 54 (46.6%) were male (Table 1). Vaccination information was available for 88 persons with event-associated cases, 85 (96.6%) completed vaccination, including five who had received a booster dose. Among event-associated cases, the median interval from completing primary vaccination series to positive test result was 210 days (IQR = 193–232 days), and from booster dose to positive test result was 14 days (IQR = 12–20 days). Among the 3,630 (80%) test-negative attendees who completed primary vaccination or received booster dose, the median interval from completion of primary vaccination series to test date was 207 days (IQR = 187–225 days) and from receipt of booster dose to test date was 34 days (IQR = 22–66 days). One attendee with event-associated COVID-19 was hospitalized; no deaths were reported.

Genomic sequencing of 20 specimens identified the Delta variant (AY.25 and AY.103 sublineages) in 15 (75%) cases, and the Omicron variant (BA.1 sublineage) in five (25%). All attendees with Omicron cases were part of a known epidemiologic and phylogenetic cluster (2); no Delta variant cases were part of a cluster.^†††

Among 7,259 respondents from the online survey (approximately 21% response rate) across 48 jurisdictions, 4,259 attendees reported receiving a COVID-19 test during November 18–December 5, 2021 (Table 2). Among these, 48 (1.1%) respondents from 10 jurisdictions reported SARS-CoV-2 infections during the investigation date range (including six from self-tests). The median age among test-positive attendees was 28 years (IQR = 23.0–35.0 years), 13 (27.7%) of 47 with reported gender were male, 15 (32.6%) of 46 with reported race/ethnicity were non-Hispanic White, and 19 (42.2%) of 45 reporting residency were New York residents. Among 47 test-positive survey respondents reporting vaccination information, 37 (78.7%) completed a primary vaccination series, six (12.8%) received a booster dose, and four (8.5%) were partially vaccinated. Among 4,157 test-negative respondents, 2,274 (54.7%) completed primary vaccination, 1,511 (36.3%) received a booster dose, and 372 (8.9%) were partially vaccinated. The median interval from booster dose receipt to a SARS-CoV-2–positive specimen was 12 days (IQR = 10–21 days) and to a negative specimen was 20 days (IQR = 10–35 days).

Among the 48 test-positive respondents, 34 (70.8%) reported COVID-19 compatible symptoms, compared with 312 (7.4%) of 4,203 test-negative respondents. Nasal congestion or runny nose (91.2%) and fatigue (88.2%) were common symptoms reported among test-positive respondents; among test-negative respondents, nasal congestion or runny nose (223 of 310; 71.9%) and sore throat (191 of 305; 62.6%) were most commonly reported. No hospitalizations were reported.

Test-positive survey respondents reported engaging in certain activities more frequently than did test-negative respondents, including attending bars (16.7% versus 6.9%), karaoke (18.8% versus 2.4%), or nightclubs (10.4% versus 3.0%) outside of the convention, and eating or drinking indoors near others for at least 15 minutes at the convention (62.5% versus 43.7%) (all p<0.05). Differences were also found in reporting close contact with someone with a positive COVID-19 test result within 10 days of symptom onset or test result (44.1% versus 6.0%) (p<0.05). Most (4,041 [95.2%]) attendees, reported always wearing a mask over their nose and mouth while indoors; no difference was found in type of mask used by test result. Among 4,245 survey respondents, 87 (2.0%) reported knowing at least one person (mean = 2.4) whom they met, interacted with, or worked with during the event who received a positive SARS-CoV-2 test result since attending the event.

On December 2, 2021, after identification of the first Omicron case, CDC issued an Epidemic Information Exchange (Epi-X) notification to U.S. health departments to identify COVID-19 cases among event attendees. On December 3, 2021, the NYC Test and Trace program^§§§ alerted registered attendees via text and email messages to get tested immediately, wear a face mask, and maintain physical distance from others.

Acknowledgments

Ben Brumfield, Sheryl Roehl, Mona Byrkit, Nicole Fehrenbach, Anna Llewellyn, Rieza Soelaeman, Alicia Dunajcik, Charles Braxton, Chisom Onyeuku, Christina Winfield, Cody Bennett, Denise Sheriff, Francisco Palomeque, Geremy Lloyd, Isaa Lee-Hall, Laird Ruth, Laura Hill, Lauren Billick, Namita Agravat, Neela Persad, Otto Ike, Rebecca Sabo, Robert Amy, Tomi Ademokun, Veneranda Ngulefac, CDC COVID-19 Emergency Response Team; Clarion Events; Shama Ahuja, Jennifer Baumgartner, Elizabeth Luoma, Emily McGibbon, Don Weiss, New York City Department of Health and Mental Hygiene; New York City Test and Trace Corps; Stella Tsai, Troy Brancard, Lindsay Lowe, New Jersey Department of Health; Lynn Sosa, Connecticut Department of Public Health; Jyoti Narayana, Marilee Kellis Butterfield, Arizona Department of Health Services; Christian Santiago, Puerto Rico Department of Health; Kirsten St. George, Jennifer Laplante, Patrick Bryant, Amy Dean, Meghan Fuschino, Alexis Russell, New York State Department of Health.

Corresponding author: Libby Horter, qsw2@cdc.gov.

¹CDC COVID-19 Emergency Response Team; ²Goldbelt C6, LLC, Chesapeake, Virginia; ³Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; ⁴New York City Department of Health and Mental Hygiene, New York; ⁵New York State Department of Health; ⁶Minnesota Department of Health; ⁷Connecticut Department of Public Health; ⁸Epidemic Intelligence Service, CDC; ⁹Massachusetts Department of Public Health; ¹⁰Pennsylvania Department of Health; ¹¹CSTE Applied Fellow, Council State and Territorial Epidemiologists, Atlanta, Georgia; ¹²Philadelphia Department of Public Health, Philadelphia, Pennsylvania; ¹³Division of Disease Control and Health Protection, Florida Department of Health; ¹⁴New Jersey Department of Health; ¹⁵Rhode Island Department of Health; ¹⁶North Carolina Department of Health and Human Services; ¹⁷Delaware Division of Public Health, Dover, Delaware; ¹⁸Virginia Department of Health; ¹⁹California Department of Public Health; ²⁰South Carolina Department of Health & Environmental Control; ²¹Michigan Department of Health and Human Services; ²²Tennessee Department of Health; ²³Division of State and Local Readiness, Office of Public Health Preparedness and Response, CDC; ²⁴Wisconsin Department of Health Services; ²⁵Arizona Department of Health Services; ²⁶Chicago Department of Public Health, Chicago, Illinois; ²⁷Nevada Department of Health and Human Services; ²⁸Hawaii State Department of Health; ²⁹Missouri Department of Health and Senior Services; ³⁰Arkansas Department of Health; ³¹Colorado Department of Public Health and Environment; ³²Idaho Department of Health and Welfare; ³³Ohio Department of Health;³⁴Indiana Department of Health; ³⁵CDC Foundation, Atlanta, Georgia; ³⁶Kentucky Department of Health; ³⁷Maine Department of Health and Human Services; ³⁸New Hampshire Division of Public Health Services; ³⁹Utah Department of Health; ⁴⁰West Virginia Department of Health & Human Resources; ⁴¹Mississippi State Department Health; ⁴²State of Montana Department of Health and Human Services;⁴³Nebraska Department of Health and Human Services; ⁴⁴Puerto Rico Department of Health; ⁴⁵North Dakota Department of Health.

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FIGURE. Event-associated cases* of SARS-CoV-2 infection (n = 119)^† among attendees of a large indoor convention in New York City, by date of specimen collection and test type^§ — 16 jurisdictions, November–December 2021

Abbreviation: RT-PCR = reverse transcription–polymerase chain reaction.

* Reported by health department COVID-19 surveillance systems.

^† Among 4,560 attendees with test result data, 119 (2.6%) event-associated cases were identified by January 6, 2022, from 16 jurisdictions.

^§ Antigen, RT-PCR, and RT-PCR and antigen are mutually exclusive groups.

Abbreviation: NA = not applicable.
* Testing for statistical significance was conducted using nonparametric tests (i.e., Wilcoxon rank-sum) to compare continuous data and Pearson’s chi-square or Fisher’s exact test to compare categorical data. Statistical significance was defined as p<0.05.
^† “Known no.” is defined as number of persons for individual variables that did not have missing data.
^§ Percentage among those who received a booster dose.
^¶ Percentage among those who received a primary vaccination series.

Abbreviations: NA = not applicable; NYC = New York City.
* Self-reported SARS-CoV-2 test results from an online, anonymous survey.
^† Testing for statistical significance was conducted using nonparametric tests (i.e., Wilcoxon rank-sum) to compare continuous data and Pearson’s chi-square or Fisher’s exact test to compare categorical data. Statistical significance was defined as p<0.05.
^§ Known no. is defined as number of persons for individual variables that did not have missing data.
^¶ Other is defined in the survey as “none of these.”
** COVID Alert NYC app is a voluntary, anonymous, exposure-notification smartphone application that provides an alert if a person was in close contact with someone who receives a positive SARS-CoV-2 test result. The period for exposure notification was November 18–December 5, 2021.