Objectives: The aim of this analysis was to describe nirmatrelvir/ritonavir real-world effectiveness in preventing hospitalization among high-risk US COVID-19 patients during SARS-CoV-2 Omicron predominance. Design: An ongoing population-based cohort study with retrospective and prospective collection of electronic healthcare data in the United States. Methods: Data for this analysis were collected from the US Optum de-identified COVID-19 Electronic Health Record (EHR) dataset during December 22, 2021 to June 8, 2022. Key eligibility criteria for inclusion in the database analysis were at least 12-years-old; positive SARS-CoV-2 test, COVID-19 diagnosis, or nirmatrelvir/ritonavir prescription; and high risk of severe COVID-19 based on demographic/clinical characteristics. Potential confounders between groups were balanced using propensity score matching (PSM). Immortal time bias was addressed. Outcome measures: Hospitalization rates within 30 (primary analysis) or 15 (sensitivity analysis) days from COVID-19 diagnosis overall and within subgroups were evaluated. Results: Before PSM, the nirmatrelvir/ritonavir group (n=2811) was less racially diverse, older, and had higher COVID-19 vaccination rates and a greater number of comorbidities than the non-nirmatrelvir/ritonavir group (n=194,542). Baseline characteristics were well balanced across groups (n=2808 and n=10,849, respectively) after PSM. Incidence of hospitalization (95% CI) within 30 days was 1.21% (0.84%, 1.69%) for the nirmatrelvir/ritonavir group and 6.94% (6.03%, 7.94%) for the non-nirmatrelvir/ritonavir group, with a hazard ratio (95% CI) of 0.16 (0.11, 0.22; 84% relative risk reduction). Incidence within 15 days was 0.78% (0.49%, 1.18%) for the nirmatrelvir/ritonavir group and 6.54% (5.65%, 7.52%) for the non-nirmatrelvir/ritonavir group; hazard ratio 0.11 (0.07, 0.17; 89% relative risk reduction). Nirmatrelvir/ritonavir was effective in African American patients (hazard ratio, 0.35 [0.15, 0.83]; 65% relative risk reduction). Relative risk reductions were comparable with overall results across ages and among vaccinated patients. Conclusions: Real-world nirmatrelvir/ritonavir effectiveness against hospitalization during the Omicron era supports EPIC-HR efficacy among high-risk patients. Future research should confirm these early real-world results and address limitations.

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Background: Although stroke is an uncommon but life-threatening complication among spinal surgery patients, the recognition of this adverse event is critical given the aging population undergoing surgical procedures. The objective of this study was to estimate the incidence of stroke among adults undergoing elective posterior lumbar fusion (PLF) during post-operative risk windows and among different subgroups. Methods: A retrospective cohort study using a longitudinal electronic healthcare record (EHR) database was conducted from January 1, 2007 to June 30, 2018. Elective PLF, stroke, and select clinical characteristics were defined based on International Classification of Disease codes. Patients aged 18 to 85 years with ≥ 183 days of enrollment in the database prior to undergoing elective PLF were followed from the index date until the occurrence of stroke, death, loss to follow-up, or end of study period, whichever occurred first. Incidence proportions (IPs) and rates (IRs) of stroke were estimated in the following risk windows: index hospitalization, ≤ 30 days, ≤ 90 days, ≤ 180 days, and ≤ 365 days post-operation Results: A total of 43,063 patients were eligible for the study. The IP of stroke following elective PLF ranged from 0.29% (95% confidence interval [CI]: 0.25%, 0.35%) during index hospitalization to 1.12% (95% CI: 1.03%, 1.23%) ≤ 365 days post-operation; the IR of stroke following elective PLF per 1000 person-years decreased consistently from 229.08 (95% CI: 192.38, 272.78) during index hospitalization to 13.68 (95% CI: 12.51, 14.96) ≤ 365 days post-operation. Stratified analyses revealed that older patients had a higher incidence of stroke. Additionally, black patients had higher stroke incidences than white, Asian, or other patients. Furthermore, the incidence of post-operative stroke was higher among patients with a history of type 2 diabetes than among patients without such history. Conclusions: The incidence of stroke following elective PLF found here using an EHR database is slightly higher than that reported in the literature; however, the discrepancy is due to differences in the variable definitions, study populations, follow-up periods, and data sources between our study and those in the literature.