Comparative performance of multiplex salivary and commercially available serologic assays to detect SARS-CoV-2 IgG and neutralization titers.

Oral fluid (hereafter saliva) offers a non-invasive sampling method for detection of SARS-CoV-2 antibodies. However, data comparing performance of salivary tests against commercially-available serologic and neutralizing antibody (nAb) assays are lacking. This study compared the performance of a laboratory-developed multiplex salivary SARS-CoV-2 IgG assay targeting antibodies to nucleocapsid (N), receptor binding domain (RBD) and spike (S) antigens to three commercially-available SARS-CoV-2 serologic enzyme immunoassays (EIAs) (Ortho Vitros, Euroimmun, and BioRad) and nAb. Paired saliva and plasma samples were collected from 101 eligible COVID-19 convalescent plasma (CCP) donors >14 days since PCR+ confirmed diagnosis. Concordance was evaluated using positive (PPA) and negative (NPA) percent agreement, and Cohen's kappa coefficient. The range between salivary and plasma EIAs for SARS-CoV-2-specific N was PPA: 54.4-92.1% and NPA: 69.2-91.7%, for RBD was PPA: 89.9-100% and NPA: 50.0-84.6%, and for S was PPA: 50.6-96.6% and NPA: 50.0-100%. Compared to a plasma nAb assay, the multiplex salivary assay PPA ranged from 62.3% (N) and 98.6% (RBD) and NPA ranged from 18.8% (RBD) to 96.9% (S). Combinations of N, RBD, and S and a summary algorithmic index of all three (N/RBD/S) in saliva produced ranges of PPA: 87.6-98.9% and NPA: 50-91.7% with the three EIAs and ranges of PPA: 88.4-98.6% and NPA: 21.9-34.4% with the nAb assay. A multiplex salivary SARS-CoV-2 IgG assay demonstrated variable, but comparable performance to three commercially-available plasma EIAs and a nAb assay, and may be a viable alternative to assist in monitoring population-based seroprevalence and vaccine antibody response.

The Experience of 2 Independent Schools With In-Person Learning During the COVID-19 Pandemic.

BACKGROUND: In 2020, US schools closed due to SARS-CoV-2 but their role in transmission was unknown. In fall 2020, national guidance for reopening omitted testing or screening recommendations. We report the experience of 2 large independent K-12 schools (School-A and School-B) that implemented an array of SARS-CoV-2 mitigation strategies that included periodic universal testing. METHODS: SARS-CoV-2 was identified through periodic universal PCR testing, self-reporting of tests conducted outside school, and contact tracing. Schools implemented behavioral and structural mitigation measures, including mandatory masks, classroom disinfecting, and social distancing. RESULTS: Over the fall semester, School-A identified 112 cases in 2320 students and staff; School-B identified 25 cases (2.0%) in 1400 students and staff. Most cases were asymptomatic and none required hospitalization. Of 69 traceable introductions, 63 (91%) were not associated with school-based transmission, 59 cases (54%) occurred in the 2 weeks post-thanksgiving. In 6/7 clusters, clear noncompliance with mitigation protocols was found. The largest outbreak had 28 identified cases and was traced to an off-campus party. There was no transmission from students to staff. CONCLUSIONS: Although school-age children can contract and transmit SARS-CoV-2, rates of COVID-19 infection related to in-person education were significantly lower than those in the surrounding community. However, social activities among students outside of school undermined those measures and should be discouraged, perhaps with behavioral contracts, to ensure the safety of school communities. In addition, introduction risks were highest following extended school breaks. These risks may be mitigated with voluntary quarantines and surveillance testing prior to reopening.

Outcomes of Nursing Home COVID-19 Patients by Initial Symptoms and Comorbidity: Results of Universal Testing of 1970 Residents.

OBJECTIVE: Clinical implications of asymptomatic cases of the novel coronavirus disease 2019 (COVID-19) in nursing homes remain poorly understood. We assessed the association of symptom status and medical comorbidities on mortality and hospitalization risk associated with COVID-19 in residents across 15 nursing homes in Maryland. DESIGN: Retrospective cohort study. SETTING AND PARTICIPANTS: 1970 residents from 15 nursing home facilities with universal COVID-19 testing in Maryland. METHODS: We used descriptive statistics to compare baseline characteristics, logistic regression to assess the association of comorbidities with COVID-19, and Cox regression to assess the association of asymptomatic and symptomatic COVID-19 with mortality and hospitalization. We assessed the association of comorbidities with mortality and hospitalization risk. Symptom status was assessed at the time of the first test. Maximum follow-up was 94 days. RESULTS: Among the 1970 residents (mean age 73.8, 57% female, 68% black), 752 (38.2%) were positive on their first test. Residents who were positive for COVID-19 and had multiple symptoms at the time of testing had the highest risk of mortality [hazard ratio (HR) 4.44, 95% confidence interval (CI) 2.97, 6.65) and hospitalization (subhazard ratio 2.38, 95% CI 1.70, 3.33), even after accounting for comorbidity burden. Cases who were asymptomatic at testing had a higher risk of mortality (HR 2.92, 95% CI 1.95, 4.35) but not hospitalization (HR 1.06, 95% CI 0.82, 1.38) compared with those who were negative for COVID-19. Of 52 SARS-CoV-2-positive residents who were asymptomatic at the time of testing and were closely monitored for 14 days at one facility, only 6 (11.6%) developed symptoms. CONCLUSIONS AND IMPLICATIONS: Asymptomatic infection with SARS-CoV-2 in the nursing home setting was associated with increased risk of death, suggesting a need for closer monitoring of these residents, particularly those with underlying cardiovascular and respiratory comorbidities.