Use of Serial Testing to Interrupt a SARS-CoV-2 Outbreak on a Hospital Medical Floor - Minnesota, October-December 2020.

OBJECTIVE: Describe a SARS-CoV-2 hospital outbreak and the role of serial testing of patients and healthcare personnel (HCP) in interrupting transmission. DESIGN: Outbreak investigation. SETTING: Medical floor of a tertiary care center in Minnesota. METHODS: Serial testing for SARS-CoV-2 and whole genome sequencing (WGS) of positive specimens from HCP and patients was used. An outbreak-associated case was defined as a positive SARS-CoV-2 molecular test in HCP who worked on the floor prior to testing positive or in a patient who was hospitalized on the medical floor during October 27-December 1, 2020. WGS was used to understand potential routes of transmission. RESULTS: The outbreak was detected after a patient hospitalized for 12 days tested positive for SARS-CoV-2. Serial testing of patients and HCP was conducted in response. Overall, 247 HCP and 41 patients participated in serial SARS-CoV-2 testing. Fifty-two (21%) HCP and 19 (46%) hospitalized patients tested positive. One additional HCP tested positive outside of serial testing. WGS of specimens from 27 (51%) HCP and 15 (79%) patients identified three distinct transmission clusters. WGS and epidemiologic evidence suggested intrafacility transmission. The proportion of asymptomatic and pre-symptomatic patients who tested positive (63%) and HCP who worked during their infectious period (75%) highlight the need for serial testing of asymptomatic patients and HCP during outbreaks. CONCLUSIONS: Coupled with preventive measures such as personal protective equipment use and physical distancing, serial testing of HCP and patients could help detect and prevent transmission within healthcare facilities during outbreaks and when nosocomial transmission is suspected.

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

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.

Characteristics of COVID-19 Vaccine Breakthrough Cases in Minnesota, 2021

Background Over 600,000 COVID-19 cases, including >7000 deaths reported to MN Dept of Health (MDH) by June 1, 2021. Clinical trials demonstrated high effectiveness of COVID vaccines. We assessed COVID-19 cases among fully vaccinated residents [vaccine breakthrough (VB) cases]. Methods COVID-19 VB cases were MN residents with completed COVID-19 vaccination series ≥14 days prior to symptom onset or positive for SARS-CoV-2 by nucleic acid amplification or antigen test. COVID-19 cases were reported to MDH and COVID-19 vaccinations reported to the MN Immunization Information Connection (MIIC). COVID-19 cases were matched to MIIC to identify VB and interviewed;medical records of hospitalized cases were reviewed. Available VB case specimens underwent whole genome sequencing (WGS) at MDH or collaborating lab. Results Jan 19 – June 1, 2021, 2765 VB cases were reported among >2.45 million fully vaccinated residents and 147,445 COVID-19 cases. VB case median (MED) age was 52 y (IQR 38, 68), 83% white, 65% female;MED age of fully vaccinated was 55 y (IQR 30, 68), 77% white, 54% female. Of VB cases, 273 (10%) were hospitalized and 32 (1%) died (MED age 74 y;IQR 66, 85). 2212 (80%) VB cases were interviewed;60% reported symptoms;most common were fatigue (53%), rhinorrhea (49%), cough (42%), headache (41%). 35% reported a comorbidity. Of hospitalized VB cases, 120 had completed record reviews. 64 were admitted for COVID-19 related illness (MED age 74 y, IQR:65, 83) including 27 admitted to ICU (MED age 71 y, IQR: 65, 83). 90% (108) reported a comorbidity, most common being chronic metabolic conditions (46%), obesity (45%), renal disease (31%) and chronic lung disease (26%);27 were immunocompromised (not mutually exclusive), including immunosuppressive therapy (15), hematological malignancy (9), other cancer (11), and organ transplant recipients (8). Of 604 VB case specimens, 79% were B.1.1.7, 9% B.1.427/429, 3% P.1, and 2% B.1.351;lineage distribution was similar to overall 24,157 MN SARS-CoV2 WGS data. Conclusion Identified VB cases were 0.1% of those vaccinated and < 2% of total cases reported in the time period. COVID-19 vaccines are an important tool in preventing COVID-19. Additional surveillance, including WGS and case characteristics will be useful to monitor VB. Disclosures Ruth Lynfield, MD, Nothing to disclose

First Identified Cases of SARS-CoV-2 Variant P.1 in the United States - Minnesota, January 2021.

Since December 2020, the Minnesota Department of Health (MDH) Public Health Laboratory has been receiving 100 specimens per week (50 from each of two clinical partners) with low cycle threshold (Ct) values for routine surveillance for SARS-CoV-2, the virus that causes COVID-19. On January 25, 2021, MDH identified the SARS-CoV-2 variant P.1 in one specimen through this surveillance system using whole genome sequencing, representing the first identified case of this variant in the United States. The P.1 variant was first identified in travelers from Brazil during routine airport screening in Tokyo, Japan, in early January 2021 (1). This variant has been associated with increased transmissibility (2), and there are concerns that mutations in the spike protein receptor-binding domain might disrupt both vaccine-induced and natural immunity (3,4). As of February 28, 2021, a total of 10 P.1 cases had been identified in the United States, including the two cases described in this report, followed by one case each in Alaska, Florida, Maryland, and Oklahoma (5).

COVID-19 Outbreak Associated With a Fitness Center-Minnesota, September-November 2020.

The Minnesota Department of Health investigated a coronavirus disease 2019 (COVID-19) outbreak at a fitness center in Olmsted County, Minnesota. Twenty-three severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections (5 employees and 18 members) were identified. An epidemiological investigation supported by whole genome sequencing demonstrated that transmission of SARS-CoV-2 occurred at the fitness center despite following recommended prevention strategies.

First Identified Cases of SARS-CoV-2 Variant B.1.1.7 in Minnesota - December 2020-January 2021.

On January 9, 2021, the Minnesota Department of Health (MDH) announced the identification of the SARS-CoV-2 variant of concern (VOC) B.1.1.7, also referred to as 20I/501Y.V1 and VOC 202012/01, in specimens from five persons; on January 25, MDH announced the identification of this variant in specimens from three additional persons. The B.1.1.7 variant, which is reported to be more transmissible than certain other SARS-CoV-2 lineages*,† (1), was first reported in the United Kingdom in December 2020 (1). As of February 14, 2021, a total of 1,173 COVID-19 cases of the B.1.1.7 variant had been identified in 39 U.S. states and the District of Columbia (2). Modeling data suggest that B.1.1.7 could become the predominant variant in the United States in March 2021 (3).