CDC’s 2023 Epidemic Intelligence Service (EIS) Conference brought together approximately 1,800 in-person and 400 virtual attendees during April 24–27, 2023, in a hotel conference facility in Atlanta, Georgia. This annual, multi-purpose event consists of both traditional scientific presentations, as well as one-on-one and small-group recruitment events for incoming EIS officers and staff from CDC and state and local health departments.

On Thursday, April 27, several in-person attendees notified conference organizers that they had tested positive for SARS-CoV-2, the virus that causes COVID-19. That same day, EIS leaders made an announcement at the conference about potential cases and took action to reduce further spread connected with the conference and related events. After the conference ended, CDC received additional reports of attendees testing positive for SARS-CoV-2 and worked with the Georgia Department of Public Health to initiate a rapid assessment. The goals were to learn more about transmission that occurred and add to our understanding as we transition to the next phase of COVID-19 surveillance and response.

The rapid assessment team surveyed in-person attendees from May 5–12 about their COVID-19 testing results and healthcare-seeking behavior. Among 1,443 survey respondents (over 80% of the in-person attendees):

• 181 (13%) respondents reported testing positive for SARS-CoV-2
• Of those who reported testing positive, 52% reported no known prior COVID-19 infection
• 1,435 (99.4%) of respondents reported at least one COVID-19 vaccine dose
• 49 (27%) of the respondents who tested positive received antiviral medications
• 70% of respondents reported not wearing a mask; the event coincided with a period of low COVID-19 Community Levels, where masking is not recommended in CDC guidance
• None were hospitalized

These findings underline the importance of vaccination for protecting individuals against severe illness and death related to COVID-19. Nearly every respondent reported receiving at least one COVID-19 vaccine dose, and none of the 181 people who reported testing positive were hospitalized.

Not surprisingly, there was an increased chance of infection the longer participants attended the conference and the more events they participated in. Specifically, respondents who tested positive reported attending the conference on average for all four days, and the risk of infection was 70% greater among those who attended for three or more days versus those who attended for two or fewer days.

Again, the findings of this rapid assessment support previous data that demonstrate that COVID-19 vaccines, antiviral treatments, and immunity from previous infection continue to provide people with protection against serious illness. CDC continues to recommend that everyone ages six months and older stay up to date with all COVID-19 vaccines, including receiving an updated vaccine. COVID-19 vaccines are effective at protecting people from getting seriously ill, being hospitalized, and dying.