In this investigation, a confirmed case in a household contact was defined as having received a positive SARS-CoV-2 nucleic acid amplification test result or antigen test result ≤14 days after the index date (date of the index patient's symptom onset or positive SARS-CoV-2 nucleic acid amplification test result or antigen test result), and a probable case in a household contact was defined as the presence of COVID-19-compatible symptoms during the same 14-day period but without a positive SARS-CoV-2 test confirmation. Persons without symptoms and who did not have a positive SARS-CoV-2 test result were not considered to have a case of COVID-19. Analysis of AR among household contacts excluded eight persons with unknown case status (persons for whom it was not known whether COVID-19-compatible symptoms were present and whether SARS-CoV-2 testing had occurred [or if testing occurred, the results were unknown]).

Early studies suggest that COVID-19 vaccines protect against severe illness (1); however, postvaccination SARS-CoV-2 infections (i.e., breakthrough infections) can occur because COVID-19 vaccines do not offer 100% protection (2,3). Data evaluating the occurrence of breakthrough infections and impact of vaccination in decreasing transmission in congregate settings are limited. Skilled nursing facility (SNF) residents and staff members have been disproportionately affected by SARS-CoV-2, the virus that causes COVID-19 (4,5), and were prioritized for COVID-19 vaccination (6,7). Starting December 28, 2020, all 78 Chicago-based SNFs began COVID-19 vaccination clinics over several weeks through the federal Pharmacy Partnership for Long-Term Care Program (PPP). † In February 2021, through routine screening, the Chicago Department of Public Health (CDPH) identified a SARS-CoV-2 infection in a SNF resident >14 days after receipt of the second dose of a two-dose COVID-19 vaccination series. SARS-CoV-2 cases, vaccination status, and possible vaccine breakthrough infections were identified by matching facility reports with state case and vaccination registries. Among 627 persons with SARS-CoV-2 infection across 75 SNFs since vaccination clinics began, 22 SARS-CoV-2 infections were identified among 12 residents and 10 staff members across 15 facilities ≥14 days after receiving their second vaccine dose (i.e., breakthrough infections in fully vaccinated persons). Nearly two thirds (14 of 22; 64%) of persons with breakthrough infections were asymptomatic; two residents were hospitalized because of COVID-19, and one died. No facility-associated secondary transmission occurred. Although few SARS-CoV-2 infections in fully vaccinated persons were observed, these cases demonstrate the need for SNFs to follow recommended routine infection prevention and control practices and promote high vaccination coverage among SNF residents and staff members.CDPH monitors SNF SARS-CoV-2 infections using a data triangulation method that matches the SARS-CoV-2 test results from nucleic acid amplification tests (NAATs, such as reverse transcription-polymerase chain reaction [RT-PCR]) and antigen tests reported to the Illinois' National Electronic Disease Surveillance System with facility-reported line lists of SARS-CoV-2 test results from routine screening testing. § In February 2021, CDPH began matching records to Illinois' Comprehensive Automated Immunization Registry Exchange to identify breakthrough infections. After identifying SARS-CoV-2 infection in a SNF resident 16 days after receipt of a second vaccine dose, CDPH initiated an investigation to quantify breakthrough infections across all facilities, evaluate symptoms and clinical outcomes, and assess potential secondary transmission. Vaccine effectiveness was not evaluated. * These authors contributed equally to this report. † A public-private partnership among CDC; CVS Pharmacy; Managed Health Care Associates, Inc.; and Walgreens to provide on-site COVID-19 vaccination of residents and staf...

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On October 27, 2020, this report was posted as an MMWR Early Release on the MMWR website (https://www.cdc.gov/mmwr). Data on transmission of SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19), among college athletes are limited. In August 2020, the Chicago Department of Public Health (CDPH) was notified of a cluster of COVID-19 cases among a university's men's and women's soccer teams. CDPH initiated an investigation, interviewed members of both teams, and collated laboratory data to understand transmission of SARS-CoV-2 within the teams. Numerous social gatherings with limited mask use or social distancing preceded the outbreak. Transmission resulted in 17 laboratory-confirmed COVID-19 cases across both teams (n = 45), likely from a single source introduction of SARS-CoV-2 (based on whole genome sequencing) and subsequent transmission during multiple gatherings. Colleges and universities are at risk for COVID-19 outbreaks because of shared housing and social gatherings where recommended prevention guidance is not followed. Improved strategies to promote mask use and social distancing among college-aged adults need to be implemented, as well as periodic repeat testing to identify asymptomatic infections and prevent outbreaks among groups at increased risk for infection because of frequent exposure to close contacts in congregate settings on and off campus. Investigation and Results University A student athletes returned to campus* during June and were required to have two negative real-time reverse transcription-polymerase chain reaction (RT-PCR) SARS-CoV-2 tests before participating in any preseason training activities. Voluntary training sessions for both soccer teams began in July. In August, a member of the men's soccer team reported COVID-19-related symptoms to coaching staff members (Figure). The student reported attending several social gatherings with teammates in the preceding 14 days, including a birthday party and an unsanctioned soccer match between the men's and women's teams. Over the next 2 days, five other soccer players reported symptoms, and both teams were instructed to isolate or quarantine. † Specimens * University policy limited on-campus congregating and gatherings and required mask use in all settings (except personal residence), social distancing, and daily health screening. † The term "quarantine" is used to describe the 14-day period after a person who might have been exposed to COVID-19 stays away from others. The term "isolation" is used to describe the 10-day period when a person stays away from others after that person experiences symptom onset or receives a positive SARS-CoV-2 test result.

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