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. 2022 Feb 1;5(2):e220536.
doi: 10.1001/jamanetworkopen.2022.0536.

Transmission of and Infection With COVID-19 Among Vaccinated and Unvaccinated Attendees of an Indoor Wedding Reception in Minnesota

Haley Wienkes  1 , Kelley Vilen  1 , Alexandra Lorentz  1   2 , Daniel Gerlach  1 , Xiong Wang  1 , Amy Saupe  1 , Richard Danila  1 , Ruth Lynfield  1 , Kirk Smith  1 , Carlota Medus  1
Affiliations

Transmission of and Infection With COVID-19 Among Vaccinated and Unvaccinated Attendees of an Indoor Wedding Reception in Minnesota

Haley Wienkes et al. JAMA Netw Open. .

Abstract

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.

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Conflict of interest statement

Conflict of Interest Disclosures: Dr Lynfield reported serving as associate editor for the American Academy of Pediatrics Report of the Committee on Infectious Diseases (Red Book), with fee donated to the Minnesota Department of Health. No other disclosures were reported.

Figures

Figure 1.
Figure 1.. Epidemic Curve of Onset Dates of Index, Primary, and Secondary Cases
Figure 2.
Figure 2.. Whole Genome Sequencing Results With Onset as Days Since Wedding
All sequences were the Delta variant. Branches are labeled by single-nucleotide variant (SNV) differences. Interactive Tree of Life version 6.3 was used to make this visualization. aSpecific exposure date was unknown but was identified to be between day 1 and 3 after the wedding.
See this image and copyright information in PMC

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References

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