Competing Risks for Monomorphic versus Non-Monomorphic Ventricular Arrhythmias in Primary Prevention Implantable Cardioverter Defibrillator Recipients: Global Electrical Heterogeneity and Clinical Outcomes (GEHCO) Study.

BACKGROUND AND AIMS: Ablation of monomorphic ventricular tachycardia (MMVT) has been shown to reduce shock frequency and improve survival. We aimed to compare cause-specific risk factors of MMVT and polymorphic ventricular tachycardia (PVT)/ventricular fibrillation (VF) and to develop predictive models. METHODS: The multicenter retrospective cohort study included 2,668 patients (age 63.1±13.0 y; 23% female; 78% white; 43% nonischemic cardiomyopathy, left ventricular ejection fraction 28.2±11.1%). Cox models were adjusted for demographic characteristics, heart failure severity and treatment, device programming, and ECG metrics. Global electrical heterogeneity was measured by spatial QRS-T angle (QRSTa), spatial ventricular gradient elevation (SVGel), azimuth, magnitude (SVGmag), and sum absolute QRST integral (SAIQRST). We compared the out-of-sample performance of the lasso and elastic net for Cox proportional hazards and the Fine-Gray competing risk model. RESULTS: During a median follow-up of 4 years, 359 patients experienced their first sustained MMVT with appropriate ICD therapy, and 129 patients had their first PVT/VF with appropriate ICD shock. The risk of MMVT was associated with wider QRSTa (HR 1.16; 95%CI 1.01-1.34), larger SVGel (HR 1.17; 95%CI 1.05-1.30), and smaller SVGmag (HR 0.74; 95%CI 0.63-0.86) and SAIQRST (HR 0.84; 95%CI 0.71-0.99). The best-performing 3-year competing risk Fine-Gray model for MMVT (ROC(t)AUC 0.728; 95%CI 0.668-0.788) identified high-risk (> 50%) patients with 75% sensitivity, 65% specificity, and PVT/VF prediction model had ROC(t)AUC 0.915 (95%CI 0.868-0.962), both satisfactory calibration. CONCLUSION: We developed and validated models to predict the competing risks of MMVT or PVT/VF that could inform procedural planning and future RCTs of prophylactic VT ablation.

The Spatial Ventricular Gradient is Associated with Inducibility of Ventricular Arrhythmias During Electrophysiology Study.

BACKGROUND: Myocardial electrical heterogeneity is critical for normal cardiac electromechanical function, but abnormal/excessive electrical heterogeneity is proarrhythmic. The spatial ventricular gradient (SVG), a vectorcardiographic measure of electrical heterogeneity, has been associated with arrhythmic events over long-term follow-up, but its relationship with short-term inducibility of ventricular arrhythmias (VAs) is unclear. OBJECTIVE: Determine associations between SVG and inducible VAs during electrophysiology study (EPS). METHODS: Retrospective study of adults without prior sustained VA, cardiac arrest, or implantable cardioverter-defibrillator (ICD), who underwent ventricular stimulation for evaluation of syncope, non-sustained VT, and/or risk-stratification prior to primary prevention ICD implantation. 12-lead ECGs were converted into vectorcardiograms and SVG magnitude (SVGmag) and direction (azimuth and elevation) were calculated. Odds of inducible VA were regressed using logistic models. RESULTS: Among 143 patients (median age 66, 80% male, median LVEF 47%, 52% myocardial infarction), 34 (23.8%) had inducible VAs. Inducible patients had lower median LVEF (38 vs 50%, p<0.0001), smaller SVGmag (29.5 vs 39.4mV*ms, p=0.0099), and smaller cosine SVG azimuth (cosSVGaz) (0.64 vs 0.89, p=0.0007). When LVEF, SVGmag, and cosSVGaz were dichotomized at their medians, there was a 39-fold increase in adjusted odds (p=0.002) between patients with all low LVEF, SVGmag, and cosSVGaz (65% inducible), compared to patients with all high LVEF, SVGmag, and cosSVGaz (4% [n=1] inducible). After multivariable adjustment, SVGmag, cosSVGaz, and sex, but not LVEF or other characteristics, remained associated with inducible VAs. CONCLUSION: Assessment of electrical heterogeneity via SVG, which reflects abnormal electrophysiological substrate, adds to LVEF and identifies patients at high and low risk of inducible VA at EPS.

Management of patients with an electrical storm or clustered ventricular arrhythmias: a clinical consensus statement of the European Heart Rhythm Association of the ESC-endorsed by the Asia-Pacific Heart Rhythm Society, Heart Rhythm Society, and Latin-American Heart Rhythm Society.

Electrical storm (ES) is a state of electrical instability, manifesting as recurrent ventricular arrhythmias (VAs) over a short period of time (three or more episodes of sustained VA within 24 h, separated by at least 5 min, requiring termination by an intervention). The clinical presentation can vary, but ES is usually a cardiac emergency. Electrical storm mainly affects patients with structural or primary electrical heart disease, often with an implantable cardioverter-defibrillator (ICD). Management of ES requires a multi-faceted approach and the involvement of multi-disciplinary teams, but despite advanced treatment and often invasive procedures, it is associated with high morbidity and mortality. With an ageing population, longer survival of heart failure patients, and an increasing number of patients with ICD, the incidence of ES is expected to increase. This European Heart Rhythm Association clinical consensus statement focuses on pathophysiology, clinical presentation, diagnostic evaluation, and acute and long-term management of patients presenting with ES or clustered VA.

Racial and ethnic differences in uncontrolled diabetes mellitus among adults taking antidiabetic medication.

AIM: To examine whether racial and ethnic disparities in uncontrolled type 2 diabetes mellitus (T2DM) persist among those taking medication and after accounting for other demographic, socioeconomic, and health indicators. METHODS: Adults aged ≥20 years with T2DM using prescription diabetes medication were among participants assessed in a retrospective cohort study of the National Health and Nutrition Examination Survey 2007-2018. We estimated weighted sequential multivariable logistic regression models to predict odds of uncontrolled T2DM (HbA1c ≥ 8%) from racial and ethnic identity, adjusting for demographic, socioeconomic, and health indicators. RESULTS: Of 3649 individuals with T2DM who reported taking medication, 27.4% had uncontrolled T2DM (mean HgA1c 9.6%). Those with uncontrolled diabetes had a mean BMI of 33.8, age of 57.3, and most were non-Hispanic white (54%), followed by 17% non-Hispanic Black, and 20% Hispanic identity. In multivariable analyses, odds of uncontrolled T2DM among those with Black or Hispanic identities lessened, but persisted, after accounting for other indicators (Black OR 1.38, 97.5% CI: 1.04, 1.83; Hispanic OR 1.79, 97.5% CI 1.25, 2.57). CONCLUSIONS: Racial and ethnic disparities in T2DM control persisted among individuals taking medication. Future research might focus on developmental and epigenetic pathways of disparate T2DM control across racially and ethnically minoritized populations.

Impact of untreated chronic obstructive coronary artery disease on outcomes after transcatheter aortic valve replacement.

BACKGROUND AND AIMS: In transcatheter aortic valve replacement (TAVR) recipients, the optimal management of concomitant chronic obstructive coronary artery disease (CAD) remains unknown. Some advocate for pre-TAVR percutaneous coronary intervention, while others manage it expectantly. The aim of this study was to assess the impact of varying degrees and extent of untreated chronic obstructive CAD on TAVR and longer-term outcomes. METHODS: The authors conducted a retrospective cohort study of TAVR recipients from January 2015 to November 2021, separating patients into stable non-obstructive or varying degrees of obstructive CAD. The major outcomes of interest were procedural all-cause mortality and complications, major adverse cardiovascular events, and post-TAVR unplanned coronary revascularization. RESULTS: Of the 1911 patients meeting inclusion, 75%, 6%, 10%, and 9% had non-obstructive, intermediate-risk, high-risk, and extreme-risk CAD, respectively. Procedural complication rates overall were low (death 0.4%, shock 0.1%, extracorporeal membrane oxygenation 0.1%), with no difference across groups. At a median follow-up of 21 months, rates of acute coronary syndrome and unplanned coronary revascularization were 0.7% and 0.5%, respectively, in the non-obstructive population, rising in incidence with increasing severity of CAD (P < .001 for acute coronary syndrome/unplanned coronary revascularization). Multivariable analysis did not yield a significantly greater risk of all-cause mortality or major adverse cardiovascular events across groups. One-year acute coronary syndrome and unplanned coronary revascularization rates in time-to-event analyses were significantly greater in the non-obstructive (98%) vs. obstructive (94%) subsets (Plog-rank< .001). CONCLUSIONS: Transcatheter aortic valve replacement can be performed safely in patients with untreated chronic obstructive CAD, without portending higher procedural complication rates and with relatively low rates of unplanned coronary revascularization and acute coronary syndrome at 1 year.

Clinician use of the Statin Choice Shared Decision-making Encounter Tool in a Major Health System.

BACKGROUND: Effective shared decision-making (SDM) tools for use during clinical encounters are available, but, outside of study settings, little is known about clinician use of these tools in practice. OBJECTIVE: To describe real-world use of an SDM encounter tool for statin prescribing, Statin Choice, embedded into the workflow of an electronic health record. DESIGN: Cross-sectional study. PARTICIPANTS: Clinicians and their statin-eligible patients who had outpatient encounters between January 2020 and June 2021 in Cleveland Clinic Health System. MAIN MEASURES: Clinician use of Statin Choice was recorded within the Epic record system. We categorized each patient's 10-year atherosclerotic cardiovascular disease risk into low (< 5%), borderline (5-7.5%), intermediate (7.5-20%), and high (≥ 20%). Other patient factors included age, sex, insurance, and race. We used mixed effects logistic regression to assess the odds of using Statin Choice for statin-eligible patients, accounting for clustering by clinician and site. We generated a residual intraclass correlation coefficient (ICC) to characterize the impact of the clinician on Statin Choice use. KEY RESULTS: Statin Choice was used in 7% of 68,505 eligible patients. Of 1047 clinicians, 48% used Statin Choice with ≥ 1 patient, and these clinicians used it with a median 9% of their patients (interquartile range: 3-22%). In the mixed effects logistic regression model, patient age (adjusted OR per year: 1.04; 95%CI 1.03-1.04) and 10-year ASVCD risk (aOR for 5-7.5% versus < 5% risk: 1.28; 95%CI: 1.14-1.44) were associated with use of Statin Choice. Black versus White race was associated with a lower odds of Statin Choice use (aOR: 0.83; 95%CI: 0.73-0.95), as was female versus male sex (aOR: 0.83; 95%CI: 0.76-0.90). The model ICC demonstrated that 53% of the variation in use of Statin Choice was clinician-driven. CONCLUSIONS: Patient factors, including race and sex, were associated with clinician use of Statin Choice; half the variation in use was attributable to individual clinicians.

ISE/ISHNE expert consensus statement on the ECG diagnosis of left ventricular hypertrophy: The change of the paradigm.

The ECG diagnosis of LVH is predominantly based on the QRS voltage criteria. The classical paradigm postulates that the increased left ventricular mass generates a stronger electrical field, increasing the leftward and posterior QRS forces, reflected in the augmented QRS amplitude. However, the low sensitivity of voltage criteria has been repeatedly documented. We discuss possible reasons for this shortcoming and proposal of a new paradigm. The theoretical background for voltage measured at the body surface is defined by the solid angle theorem, which relates the measured voltage to spatial and non-spatial determinants. The spatial determinants are represented by the extent of the activation front and the distance of the recording electrodes. The non-spatial determinants comprise electrical characteristics of the myocardium, which are comparatively neglected in the interpretation of the QRS patterns. Various clinical conditions are associated with LVH. These conditions produce considerable diversity of electrical properties alterations thereby modifying the resultant QRS patterns. The spectrum of QRS patterns observed in LVH patients is quite broad, including also left axis deviation, left anterior fascicular block, incomplete and complete left bundle branch blocks, Q waves, and fragmented QRS. Importantly, the QRS complex can be within normal limits. The new paradigm stresses the electrophysiological background in interpreting QRS changes, i.e., the effect of the non-spatial determinants. This postulates that the role of ECG is not to estimate LV size in LVH, but to understand and decode the underlying electrical processes, which are crucial in relation to cardiovascular risk assessment.

Association of hospital spending with care patterns and mortality in patients hospitalized with community-acquired pneumonia.

BACKGROUND: Pneumonia is a leading cause of mortality and intensive therapy is costly. However, it is unclear whether more spending is associated with better patient outcomes or how hospitals could decrease costs. OBJECTIVES: This study investigates the association between hospital spending and 14-day inpatient mortality among community-acquired pneumonia inpatients. METHODS: This retrospective cohort study focused on adult pneumonia patients discharged between July 2010 and June 2015 from 260 US hospitals in the Premier database. Hospitals were divided into four pneumonia cost-of-care quartiles and average cost was calculated for each hospital. Odds of 14-day inpatient mortality and care practices were compared among high and low-cost hospitals. RESULTS: The study population comprised 534,038 patients with a mean age 69.5 (SD 16.3); 51.9% were female, 75% White, and 71.9% covered by Medicare. Hospitals were largely medium-sized (40.4%), located in the South (49.2%), and in urban areas (82.3%). The fully adjusted population-averaged cost was 14,486 US dollars (95% confidence interval [CI] 13,982-14,867). Hospital practices associated with cost included intensity of diagnostic work-up +$14 (95% CI +12 to +18; p < .0001) and de-escalation of antibiotic therapy, +$6836 (95% CI +2291 to +11,160; p = .004). There was no significant difference in odds of 14-day inpatient mortality between hospitals in the highest and lowest cost quartiles. CONCLUSIONS: Greater spending at the hospital level was not associated with lower mortality. Lower diagnostic costs were associated with lower cost of care, suggesting that judicious use of diagnostic testing might reduce costs without worsening patient outcomes.

A framework for the definition and interpretation of the use of surrogate endpoints in interventional trials.

Background: Interventional trials that evaluate treatment effects using surrogate endpoints have become increasingly common. This paper describes four linked empirical studies and the development of a framework for defining, interpreting and reporting surrogate endpoints in trials. Methods: As part of developing the CONSORT (Consolidated Standards of Reporting Trials) and SPIRIT (Standard Protocol Items: Recommendations for Interventional Trials) extensions for randomised trials reporting surrogate endpoints, we undertook a scoping review, e-Delphi study, consensus meeting, and a web survey to examine current definitions and stakeholder (including clinicians, trial investigators, patients and public partners, journal editors, and health technology experts) interpretations of surrogate endpoints as primary outcome measures in trials. Findings: Current surrogate endpoint definitional frameworks are inconsistent and unclear. Surrogate endpoints are used in trials as a substitute of the treatment effects of an intervention on the target outcome(s) of ultimate interest, events measuring how patients feel, function, or survive. Traditionally the consideration of surrogate endpoints in trials has focused on biomarkers (e.g., HDL cholesterol, blood pressure, tumour response), especially in the medical product regulatory setting. Nevertheless, the concept of surrogacy in trials is potentially broader. Intermediate outcomes that include a measure of function or symptoms (e.g., angina frequency, exercise tolerance) can also be used as substitute for target outcomes (e.g., all-cause mortality)-thereby acting as surrogate endpoints. However, we found a lack of consensus among stakeholders on accepting and interpreting intermediate outcomes in trials as surrogate endpoints or target outcomes. In our assessment, patients and health technology assessment experts appeared more likely to consider intermediate outcomes to be surrogate endpoints than clinicians and regulators. Interpretation: There is an urgent need for better understanding and reporting on the use of surrogate endpoints, especially in the setting of interventional trials. We provide a framework for the definition of surrogate endpoints (biomarkers and intermediate outcomes) and target outcomes in trials to improve future reporting and aid stakeholders' interpretation and use of trial surrogate endpoint evidence. Funding: SPIRIT-SURROGATE/CONSORT-SURROGATE project is Medical Research Council Better Research Better Health (MR/V038400/1) funded.

Reducing antimicrobial overuse through targeted therapy for patients with community-acquired pneumonia: a study protocol for a cluster-randomized factorial controlled trial (CARE-CAP).

BACKGROUND: Community-acquired pneumonia (CAP) is a significant public health concern and a leading cause of hospitalization and inpatient antimicrobial use in the USA. However, determining the etiologic pathogen is challenging because traditional culture methods are slow and insensitive, leading to prolonged empiric therapy with extended-spectrum antibiotics (ESA) that contributes to increased hospital length of stay, and antimicrobial resistance. Two potential ways to reduce the exposure to ESA are (a) rapid diagnostic assays that can provide accurate results within hours, obviating the need for empiric therapy, and (b) de-escalation following negative bacterial cultures in clinically stable patients. METHODS: We will conduct a large pragmatic 2 × 2 factorial cluster-randomized controlled trial across 12 hospitals in the Cleveland Clinic Health System that will test these two approaches to reducing the use of ESA in adult patients (age ≥ 18 years) with CAP. We will enroll over 12,000 patients and evaluate the independent and combined effects of routine use of rapid diagnostic testing at admission and pharmacist-led de-escalation after 48 h for clinically stable patients with negative cultures vs usual care. We hypothesize that both approaches will reduce days on ESA. Our primary outcome is the duration of exposure to ESA therapy, a key driver of antimicrobial resistance. Secondary outcomes include detection of respiratory viruses, treatment with anti-viral medications, positive pneumococcal urinary antigen test, de-escalation by 72 h from admission, re-escalation to ESA after de-escalation, total duration of any antibiotic, 14-day in-hospital mortality, intensive care unit transfer after admission, healthcare-associated C. difficile infection, acute kidney injury, total inpatient cost, and hospital length-of-stay. DISCUSSION: Our study aims to determine whether identifying an etiological agent early and pharmacist-led de-escalation (calling attention to negative cultures) can safely reduce the use of ESA in patients with CAP. If successful, our findings should lead to better antimicrobial stewardship, as well as improved patient outcomes and reduced healthcare costs. Our findings may also inform clinical guidelines on the optimal management of CAP. TRIAL REGISTRATION: ClinicalTrials.gov NCT05568654 . Registered on October 4, 2022.

Physical therapy provision for patients with pneumonia in US hospitals.

BACKGROUND: Physical therapy (PT) appears beneficial for hospitalized patients. Little is known about PT practice patterns and costs across hospitals. OBJECTIVE: To examine whether receiving PT is associated with specific patient and hospital characteristics for patients with pneumonia. We also explored the variability in PT service provision and costs between hospitals. METHODS: We included administrative claims from 2010 to 2015 in the Premier Healthcare Database, inclusive of 644 US hospitals. We examined associations between receiving at least one PT visit and patient (age, race, insurance, intensive care utilization, comorbidity status, and length of stay) and hospital (academic status, rurality, size, and location) characteristics. Exploratory measures included timing and proportion of days with PT visits, and per-visit and per-admission costs. RESULTS: Of 768,010 patients, 49% had PT. After adjustment, older age most significantly increased the probability of receiving PT (+38.0% if >80 vs. ≤50 years). Higher comorbidity burden, longer length of stay, and hospitalization in an urban setting were also associated with higher probability. Hospitalization in the South most significantly decreased the probability (-9.1% vs. Midwest). Patients without Medicare and Non-White patients also had lower probability. Median (interquartile range) days to first visit was 2 (1-4). Mean proportion of days with a visit was 35% ± 20%. Median per-visit cost was $88.90 [$56.70-$130.90] and per-admission was $224.00 [$137.80-$369.20]. CONCLUSION: Both clinical (intensive care utilization and comorbidity status) and non-clinical (age, race, rurality, location) factors were associated with receiving PT. Within and between hospitals, there was high variability in the number and frequency of visits, and costs.

Association between physical therapy frequency and postacute care for a national cohort of patients hospitalized with pneumonia.

BACKGROUND: Annually more than 300,000 patients hospitalized for pneumonia need postacute care. Patients and systems prefer home discharge, but physical limitations often necessitate postacute care. It is unknown whether frequency of physical therapy in the hospital affects postacute care discharges. OBJECTIVE: Examine the relationship between physical therapy visit frequency and disposition among a national sample of patients hospitalized with pneumonia. DESIGNS: Observational cohort study. SETTING: Acute care hospital. PARTICIPANTS: Adult patients with primary diagnosis of pneumonia in the Premier Data Set who received physical therapy in the hospital during a 5-day window, with therapy on at least days 1 and 5. INTERVENTION: Physical therapy visit frequency. MAIN OUTCOME AND MEASURES: Discharge disposition (home or postacute care). RESULTS: We included 18,886 patients from 595 hospitals. Just over half were discharged home (n = 9638; 51.0%) and 558 (2.95%) died. Patients getting more frequent therapy were older, non-Hispanic white, treated in small non-teaching rural hospitals in the West, Midwest, or South, and had fewer severe illness indicators. In adjusted models, patients who received physical therapy on 100% of days were 7% [(95% confidence interval, 4.3-9.7), p < .0001] more likely to go home than patients who received physical therapy on 40% of days. As a falsification test, we found that there was no relationship between physical therapy frequency and all-cause mortality. Physical therapy visit frequency was positively associated with discharge to home. Increasing visit frequency of physical therapy in hospitals might reduce the need for postacute care, but randomized controlled trials are needed to confirm the effect.

ISE/ISHNE Expert Consensus Statement on ECG Diagnosis of Left Ventricular Hypertrophy: The Change of the Paradigm. The joint paper of the International Society of Electrocardiology and the International Society for Holter Monitoring and Noninvasive Electrocardiology.

The ECG diagnosis of LVH is predominantly based on the QRS voltage criteria, i.e. the increased QRS complex amplitude in defined leads. The classical ECG diagnostic paradigm postulates that the increased left ventricular mass generates a stronger electrical field, increasing the leftward and posterior QRS forces. These increased forces are reflected in the augmented QRS amplitude in the corresponding leads. However, the clinical observations document increased QRS amplitude only in the minority of patients with LVH. The low sensitivity of voltage criteria has been repeatedly documented. We discuss possible reasons for this shortcoming and proposal of a new paradigm.

An electrophysiological substrate of COVID-19.

SARS-CoV-2 infection is associated with an increased risk of late cardiovascular (CV) outcomes. However, more data is needed to describe the electrophysiologic (EP) manifestation of post-acute CV sequelae of COVID-19. We compared two cohorts of adult patients with SARS-CoV-2 polymerase chain reaction (PCR) test and an electrocardiogram (ECG) performed between March 1, 2020, and September 13, 2020, in a retrospective double-cohort study, "Cardiovascular Risk Stratification in Covid-19" (CaVaR-Co19; NCT04555187). Patients with positive PCR comprised a COVID-19(+) cohort (n = 41; 61% women; 80% symptomatic), whereas patients with negative tests formed the COVID-19(-) cohort (n = 155; 56% women). In longitudinal analysis, comparing 3 ECGs recorded before, during, and on average 40 days after index COVID-19 episode, after adjustment for demographic and socioeconomic characteristics, baseline CV risk factors and comorbidities, use of prescription medications (including QT-prolonging drugs) before and during index COVID-19 episode, and the longitudinal changes in RR' intervals, heart rhythm, and ventricular conduction type, only in the COVID-19(+) cohort QTc increased by +30.2(95% confidence interval [CI] 0.1-60.3) ms and the spatial ventricular gradient (SVG) elevation increased by +13.5(95%CI 1.2-25.9)°. In contrast, much smaller, statistically nonsignificant changes were observed in the COVID-19(-) cohort. In conclusion, post-acute CV sequelae of SARS-CoV-2 infection manifested on ECG by QTc prolongation and rotation of the SVG vector upward.

Protection Conferred by Delta and BA.1/BA.2 Infection Against BA.4/BA.5 Infection and Hospitalization: A Retrospective Cohort Study.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 immunity has declined with subsequent waves and accrual of viral mutations. In vitro studies raise concern for immune escape by BA.4/BA.5, and a study in Qatar showed moderate protection, but these findings have yet to be reproduced. METHODS: This retrospective cohort study included individuals tested for coronavirus disease 2019 by polymerase chain reaction during Delta or BA.1/BA.2 and retested during BA.4/BA.5. The preventable fraction (PF) was calculated as ratio of the infection to the hospitalization rate for initially positive patients divided by the ratio for initially negative patients, stratified by age and adjusted for age, sex, comorbid conditions, and vaccination using logistic regression. RESULTS: A total of 20 987 patients met inclusion criteria. Prior Delta infection provided no protection against BA.4/BA.5 infection (adjusted PF, 11.9% [95% confidence interval, .8%-21.8%]); P = .04) and minimal protection against hospitalization (10.7% [4.9%-21.7%]; P = .003). In adjusted models, prior BA.1/BA.2 infection provided 45.9% (95% confidence interval, 36.2%-54.1%; P < .001) protection against BA.4/BA.5 reinfection and 18.8% (10.3%-28.3%; (P < .001) protection against hospitalization. Up-to-date vaccination provided modest protection against reinfection with BA.4/BA.5 and hospitalization. CONCLUSIONS: Prior infection with BA.1/BA.2 and up-to-date vaccination provided modest protection against infection with BA.4/BA.5 and hospitalization, while prior Delta infection provided minimal protection against hospitalization and none against infection.

Protection Against the Omicron Variant Offered by Previous Severe Acute Respiratory Syndrome Coronavirus 2 Infection: A Retrospective Cohort Study.

BACKGROUND: Previous infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) provides strong protection against future infection. There is limited evidence on whether such protection extends to the Omicron variant. METHODS: This retrospective cohort study included 635 341 patients tested for SARS-CoV-2 via polymerase chain reaction from 9 March 2020 to 1 March 2022. Patients were analyzed according to the wave in which they were initially infected. The primary outcome was reinfection during the Omicron period (20 December 2021-1 March 2022). We used a multivariable model to assess the effects of prior infection and vaccination on hospitalization. RESULTS: Among the patients tested during the Omicron wave, 30.6% tested positive. Protection of prior infection against reinfection with Omicron ranged from 18.0% (95% confidence interval [CI], 13.0-22.7) for patients infected in wave 1 to 69.2% (95% CI, 63.4-74.1) for those infected in the Delta wave. In adjusted models, previous infection reduced hospitalization by 28.5% (95% CI, 19.1-36.7), whereas full vaccination plus a booster reduced it by 59.2% (95% CI, 54.8-63.1). CONCLUSIONS: Previous infection offered less protection against Omicron than was observed in past waves. Immunity against future waves will likely depend on the degree of similarity between variants.