key: cord-0897725-g4qfeute
authors: Sami, Samira; Horter, Libby; Valencia, Diana; Thomas, Isabel; Pomeroy, Mary; Walker, Brianna; Smith-Jeffcoat, Sarah E.; Tate, Jacqueline E.; Kirking, Hannah L.; Kyaw, Nang Thu Thu; Burns, Rebecca; Blaney, Kathleen; Dorabawila, Vajeera; Hoen, Rebecca; Zirnhelt, Zachary; Schardin, Cody; Uehara, Anna; Retchless, Adam C.; Brown, Vance R.; Gebru, Yonathan; Powell, Charles; Bart, Stephen M.; Vostok, Johanna; Lund, Hannah; Kaess, Jessica; Gumke, Megan; Propper, Randy; Thomas, Deepam; Ojo, Mojisola; Green, Alison; Wieck, Morgan; Wilson, Erica; Hollingshead, Ryan J.; Nunez, Sheila V.; Saady, Dawn M.; Porse, Charsey Cole; Gardner, Kyle; Drociuk, Daniel; Scott, Julia; Perez, Taidy; Collins, Jim; Shaffner, Julie; Pray, Ian; Rust, Laura T.; Brady, Shane; Kerins, Janna L.; Teran, Richard A.; Hughes, Victoria; Sepcic, Victoria; Low, Eleanor W.; Kemble, Sarah K.; Berkley, Alexandra; Cleavinger, Kate; Safi, Haytham; Webb, Lindsey Martin; Hutton, Scott; Dewart, Courtney; Dickerson, Kristen; Hawkins, Eric; Zafar, Javeria; Krueger, Anna; Bushman, Dena; Ethridge, Bailee; Hansen, Katrina; Tant, Jake; Reed, Christy; Boutwell, Carla; Hanson, Jennifer; Gillespie, Meagan; Donahue, Matthew; Lane, Pilar; Serrano, Ruby; Hernandez, Lorena; Dethloff, Michelle A.; Lynfield, Ruth; Como-Sabetti, Kathryn; Lutterloh, Emily; Ackelsberg, Joel; Ricaldi, Jessica N.
title: Investigation of SARS-CoV-2 Transmission Associated With a Large Indoor Convention — New York City, November–December 2021
date: 2022-02-18
journal: MMWR Morb Mortal Wkly Rep
DOI: 10.15585/mmwr.mm7107a4
sha: 0a398a8d25e9a8d3c0ddca6c559a1d34c3388ffa
doc_id: 897725
cord_uid: g4qfeute

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.†.

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 eventassociated 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. † † † 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 § § § vaccinated or previously infected persons, was documented in the related cluster investigation and a previous Omicron investigation (2, 9) . The findings in this report are subject to at least six limitations. First, case finding and survey distribution were limited to a registration list of 35,613 ticket purchasers, but the event organizer reported that approximately 53,000 persons had attended. Second, matching attendees with case surveillance data was conducted by jurisdictions using only name and address, which potentially limited the number of cases and vaccination records identified or misidentified attendees. In addition, self-testing results were not included by most jurisdictions. Third, few specimens were available for sequencing (17% of event-associated cases). Fourth, the limited reach (14% of reported attendees) and low response rate of the survey (approximately 21%) can increase potential biases if respondents differ systematically from nonrespondents. Fifth, responses were subject to self-reporting bias; attendees who sought testing might be more likely to respond or respond according to social desirability bias. Finally, the definition of event-association case could have included cases from transmission unrelated to the event.

Findings from this survey and a related cluster investigation (2) of a portion of attendees suggest transmission occurred primarily among social circles and during indoor unmasked activities during the event rather than at official event activities. These findings reinforce the importance of implementing multiple, simultaneous prevention measures, such as ensuring up-todate vaccination, mask use, physical distancing, and improved ventilation in limiting SARS-CoV-2 transmission, including highly transmissible Delta and Omicron variants, during large indoor events.

What is already known about this topic?

The SARS-CoV-2 Delta (B.1.617.2) and Omicron (B.1.1.529) variants are highly transmissible. Outbreaks have been reported among vaccinated populations in indoor settings where mask use was limited.

What is added by this report?

Despite multiple introductions as evidenced by detection of at least three sublineages of SARS-CoV-2, this investigation did not find evidence of widespread transmission among a highly vaccinated population at a large event in an indoor setting where mask use was required and monitored.

What are the implications for public health practice? Implementing multiple prevention measures (vaccinations and boosters, consistent mask wearing, enhanced indoor ventilation, and testing after text notification) can limit the transmission of SARS-CoV-2 at large events, including highly transmissible variants.

alerted registered attendees via text and email messages to get tested immediately, wear a face mask, and maintain physical distance from others.

This investigation identified 119 event-associated COVID-19 cases, including one hospitalization. A parallel epidemiologic investigation describing a cluster of attendees with social links (2) revealed that at least seven U.S.-based persons potentially attended the event during their infectious period. ¶ ¶ ¶ Despite these potential exposures and multiple introductions as evidenced by genomic identification of at least three different SARS-CoV-2 variants and sublineages, findings from surveillance and survey data from a portion of attendees suggest that this large event did not lead to widespread transmission; 7-day average percentage of positive test results in NYC on December 5, 2021, (3.0%) was similar to that in this investigation (2.6%) (3). Omicron variant accounted for <5% of sequenced cases in NYC by December 4, 2021; transmission could have been higher had the convention occurred after Omicron became the dominant variant (4).

Reported prevention measures (vaccination requirements, enforcement of mask use, and avoidance of unmasked indoor settings), and a venue with HEPA filtration likely accounted for the limited number of event-associated cases. Indoor gatherings in which prevention measures do not occur have been shown to increase the spread of COVID-19 (5) (6) (7) (8) . In addition, transmission to household contacts, including to ¶ ¶ ¶ Infectious period for the cluster investigations was defined as 2 days before and 10 days after their symptom onset date.

New York; 5 New York State Department of Health; 6 Minnesota Department of Health; 7 Connecticut Department of Public Health; 8 Epidemic Intelligence Service, CDC; 9 Massachusetts Department of Public Health; 10 Pennsylvania Department of Health; 11 CSTE Applied Fellow, Council State and Territorial Epidemiologists

Rhode Island Department of Health; 16 North Carolina Department of Health and Human Services; 17 Delaware Division of Public Health

Virginia Department of Health; 19 California Department of Public Health

South Carolina Department of Health & Environmental Control; 21 Michigan Department of Health and Human Services; 22 Tennessee Department of Health

Office of Public Health Preparedness and Response, CDC; 24 Wisconsin Department of Health Services; 25 Arizona Department of Health Services; 26 Chicago Department of Public Health

Hawaii State Department of Health; 29 Missouri Department of Health and Senior Services; 30 Arkansas Department of Health; 31 Colorado Department of Public Health and Environment; 32 Idaho Department of Health and Welfare

Kentucky Department of Health; 37 Maine Department of Health and Human Services; 38 New Hampshire Division of Public Health Services; 39 Utah Department of Health; 40 West Virginia Department of Health & Human Resources; 41 Mississippi State Department Health; 42 State of Montana Department of Health and Human Services; 43 Nebraska Department of Health and Human Services; 44 Puerto Rico Department of Health

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