Top 5 Takeaways

1. High Attack Rates: The attack rate among convention attendees was 70%, but lower among their household members (33%).
2. Booster Dose Effectiveness: Fewer infections were observed among vaccinated attendees who had received a COVID-19 booster dose compared to those who had not.
3. Importance of Early Notification: Early notification and testing led to immediate quarantine or isolation, potentially reducing secondary transmission.
4. Mild Illness in Vaccinated Individuals: Despite high attack rates, the illness was relatively mild among the vaccinated cohort, with no hospitalizations or deaths reported.
5. Role of Multicomponent Prevention Measures: The investigation underscores the importance of booster doses, early notification, and other preventive measures to limit transmission and prevent severe illness.

Original Article Author and Citation

Corresponding Author

Sarah E. Smith-Jeffcoat, uyi7@cdc.gov

Suggested Citation

Smith-Jeffcoat SE, Pomeroy MA, Sleweon S, et al. Multistate Outbreak of SARS-CoV-2 B.1.1.529 (Omicron) Variant Infections Among Persons in a Social Network Attending a Convention — New York City, November 18–December 20, 2021. MMWR Morb Mortal Wkly Rep 2022;71:238–242. DOI: http://dx.doi.org/10.15585/mmwr.mm7107a3

Summary

In November 2021, a large convention in New York City with approximately 53,000 attendees led to a high attack rate of SARS-CoV-2 Omicron variant infections among a group of 30 close contacts. Despite high vaccination rates, including booster doses, the attack rate was 70% among attendees. The illness was relatively mild, and no hospitalizations or deaths were reported. Early notification and testing were crucial in mitigating further transmission.

Methods

The investigation involved interviews with 23 of the 30 close contacts, collection of demographic and clinical data, and testing for SARS-CoV-2. Both at-home antigen tests and laboratory-based tests were used. Sequencing was performed on samples to confirm the Omicron variant. Household contacts of infected attendees were also interviewed and tested.

Discussion

The high attack rates among fully vaccinated individuals highlight the Omicron variant’s partial escape from vaccine-induced immunity. However, the mild nature of the illness suggests that vaccination, including booster doses, reduces the severity of the disease. The investigation also emphasizes the importance of early notification and multicomponent prevention measures in controlling the spread of the virus.

Conclusion

This investigation reinforces the need for COVID-19 booster doses, early notification, and other preventive measures to limit transmission and prevent severe illness from the Omicron and other SARS-CoV-2 variants. The findings support the effectiveness of booster doses in reducing infection rates and highlight the role of early testing and isolation in mitigating secondary transmission.

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