Epidemiologically Linked COVID-19 Outbreaks at a Youth Camp and Men's Conference - Illinois, June-July 2021.

On June 30, 2021, the Illinois Department of Public Health (IDPH) contacted CDC concerning COVID-19 outbreaks at two events sponsored by the same organization: a 5-day overnight church camp for persons aged 14-18 years and a 2-day men's conference. Neither COVID-19 vaccination nor COVID-19 testing was required before either event. As of August 13, a total of 180 confirmed and probable cases had been identified among attendees at the two events and their close contacts. Among the 122 cases associated with the camp or the conference (primary cases), 18 were in persons who were fully vaccinated, with 38 close contacts. Eight of these 38 close contacts subsequently became infected with SARS-CoV-2, the virus that causes COVID-19 (secondary cases); among the eight close contacts with secondary cases, one half (four) were fully vaccinated. Among the 180 total persons with outbreak-associated cases, five (2.8%) were hospitalized; no deaths occurred. None of the vaccinated persons with cases were hospitalized. Approximately 1,000 persons across at least four states were exposed to SARS-CoV-2 through attendance at these events or through close contact with a person who had a primary case. This investigation underscores the impact of secondary SARS-CoV-2 transmission during large events, such as camps and conferences, when COVID-19 prevention strategies are not implemented. In Los Angeles County, California, during July 2021, when the SARS-CoV-2 B.1.617.2 (Delta) variant was predominant, unvaccinated residents were five times more likely to be infected and 29 times more likely to be hospitalized from infection than were vaccinated residents (1). Implementation of multiple prevention strategies, including vaccination and nonpharmaceutical interventions such as masking, physical distancing, and screening testing, are critical to preventing SARS-CoV-2 transmission and serious complications from COVID-19.