Risk of subsequent SARS-CoV-2 infection among vaccinated employees with or without hybrid immunity acquired early in the Omicron-predominant era of the COVID-19 pandemic.

BACKGROUND: Hybrid immunity, from COVID-19 vaccination followed by SARS-CoV-2 infection acquired after its Omicron variant began predominating, has provided greater protection than vaccination alone against subsequent infection over 1-3 months of observation. Its longer-term protection is unknown. METHODS: We conducted a retrospective cohort study of COVID-19 case incidence among healthcare personnel (HCP) mandated to be vaccinated and report on COVID-19-associated symptoms, high-risk exposures, or known-positive test results to an employee health hotline. We compared cases with hybrid immunity, defined as incident COVID-19 during the first 6 weeks of Omicron-variant predominance (run-in period), to those with immunity from vaccination alone during the run-in period. Time until COVID-19 infection over 13 subsequent months (observation period) was analyzed by standard survival analysis. RESULTS: Of 5867 employees, 641 (10.9%, 95% confidence interval [CI]: 10.1%-11.8%) acquired hybrid immunity during the run-in period. Of these, 104 (16.2%, 95% CI: 13.5%-19.3%) experienced new SARS-CoV-2 infection during the 13-month observation period, compared to 2177 (41.7%, 95% CI: 40.3%-43.0%) of the 5226 HCP without hybrid immunity. Time until incident infection was shorter among the latter (hazard ratio: 3.09, 95% CI: 2.54-3.78). CONCLUSIONS: In a cohort of vaccinated employees, Omicron-era acquired SARS-CoV-2 hybrid immunity was associated with significantly lower risk of subsequent infection over more than a year of observation-a time period far longer than previously reported and during which three, progressively more resistant, Omicron subvariants became predominant. These findings can inform institutional policy and planning for future COVID-19 additional vaccine dosing requirements for employees, for surveillance programs, and for risk modification efforts.

A Rapid Nucleic Acid Amplification Test-Based, Conditional Release-to-Work Policy for Health Care Personnel With Symptoms Consistent With COVID-19.

OBJECTIVE: Most health care personnel (HCP) reporting symptoms consistent with COVID-19 illness are assessed by high-accuracy SARS-CoV-2 assays performed in clinical laboratories, but the results of such assays typically are not available until the following day. METHODS: This is an observational study over 16 weeks of a rapid nucleic acid amplification test (NAAT) performed at point of contact. The benchmark for comparison was a simultaneously obtained specimen assayed by a routine NAAT assay performed in a clinical laboratory. RESULTS: There were 577 paired rapid and routine NAAT results. Rapid test positive predictive value was 90.0% (95% confidence interval = 88.8%-91.2%), and negative predictive value was 95.2% (95% confidence interval = 93.5%-96.9%). The rapid test avoided an estimated 160 to 184 lost work shifts over 4 months. CONCLUSIONS: A rapid NAAT test-based strategy proved effective in safely clearing symptomatic employees without infection for earlier return to work.