Key Points Question What are the characteristics of SARS-CoV-2 infection and transmission among vaccinated and unvaccinated attendees of a large indoor gathering? Findings In this cohort study of 75 individuals, nearly half of attendees at an indoor wedding reception who were tested were infected with the Delta variant of SARS-CoV-2. Unvaccinated attendees had a higher risk of SARS-CoV-2 infection than vaccinated attendees, secondary transmission from vaccinated attendees to vaccinated and unvaccinated contacts was observed, and the index case was identified as an unvaccinated symptomatic child. Meaning These findings suggest that unvaccinated people are at increased risk of contracting SARS-CoV-2 compared with vaccinated people in large social gatherings. This cohort study characterizes transmission and infection of SARS-CoV-2 among vaccinated and unvaccinated attendees of an indoor wedding reception. Importance Characterizing rates of SARS-CoV-2 infection among vaccinated and unvaccinated persons with the same exposure is critical to understanding the association of vaccination with the risk of infection with the Delta variant. Additionally, evidence of Delta variant transmission by children to vaccinated adults has important public health implications. Objective To characterize transmission and infection of SARS-CoV-2 among vaccinated and unvaccinated attendees of an indoor wedding reception. Design, Setting, and Participants This cohort study included attendees at an indoor wedding reception in Minnesota in July 2021. Data were collected from REDCap surveys and routine surveillance interviews. The full list of attendees and a partial list of emails were obtained. Fifty-seven attendees completed the emailed survey. Eighteen additional attendees were identified from the state health department COVID-19 surveillance database. Exposures Attendance at an indoor event. Main Outcomes and Measures Risk of SARS-CoV-2 infection among vaccinated and unvaccinated attendees, identification of an index case, whole genome sequencing (WGS) to identify the COVID-19 variant, understanding of transmission patterns, and assessment of secondary transmission. The primary case definition was an individual with a positive SARS-CoV-2 test who attended the wedding in the 14 days prior to their illness. Results Data were gathered for 75 attendees (mean [SE] age, 37.5 [13.7] years; 57 [76%] female individuals), of whom 56 (75%) were fully vaccinated, 4 (5%) were partially vaccinated, and 15 (20%) were unvaccinated. Of 62 attendees who were tested, 29 (47%) tested positive, including 16 of 46 fully vaccinated attendees (35%), 2 of 4 partially vaccinated attendees (50%), and 11 of 12 unvaccinated attendees (92%). Being unvaccinated was associated with a higher risk of infection compared with being vaccinated (risk ratio, 2.64; 95% CI, 1.71-4.06; P = .001). One unvaccinated adult required hospitalization. An unvaccinated child who was symptomatic on the event date was identified as the index case. Eleven specimens were available for WGS. All sequenced specimens were closely related and were identified as the Delta variant. WGS supported secondary transmission from a vaccinated individual with SARS-CoV-2. Conclusions and Relevance This cohort study identified a COVID-19 Delta variant outbreak at an indoor event despite a high proportion of vaccinated attendees. It found that vaccination was associated with a reduced risk of infection.
【초록키워드】 COVID-19, public health, SARS-CoV-2, vaccination, Hospitalization, SARS-COV-2 infection, children, Sequencing, variant, Infection, risk, Transmission, delta variant, database, cohort study, Whole genome sequencing, Characteristics, Surveillance, outbreak, symptomatic, female, age, WGS, Critical, association, Evidence, exposure, risk of infection, risk ratio, Contact, index case, evidence of, health department, Wedding Reception, Attendance, Implications, (risk ratio, state health department, higher risk, 95% CI, increased risk, reduced risk, individual, specimen, secondary transmission, measure, participant, finding, positive, SARS-CoV-2 test, vaccinated individual, whole genome, transmission patterns, being, objective, setting, Result, tested, identify, were infected, collected, sequenced, proportion, required, supported, individuals, Importance, Point, Relevance, 【제목키워드】 COVID-19,