The CRP troponin test (CTT) stratifies mortality risk in patients with non-ST elevation myocardial infarction (NSTEMI).

INTRODUCTION: The C-reactive protein (CRP)-troponin-test (CTT) comprises simultaneous serial measurements of CRP and cardiac troponin and might reflect the systemic inflammatory response in patients with acute coronary syndrome. We sought to test its ability to stratify the short- and long-term mortality risk in patients with non-ST elevation myocardial infarction (NSTEMI). METHODS: We examined 1,675 patients diagnosed with NSTEMI on discharge who had at least two successive measurements of combined CRP and cardiac troponin within 48 h of admission. A tree classifier model determined which measurements and cutoffs could be used to best predict mortality during a median follow-up of 3 years [IQR 1.8-4.3]. RESULTS: Patients with high CRP levels ( > 90th percentile, >54 mg/L) had a higher 30-day mortality rate regardless of their troponin test findings (16.7% vs. 2.9%, p < 0.01). However, among patients with "normal" CRP levels ( < 54 mg/L), those who had high troponin levels ( > 80th percentile, 4,918 ng/L) had a higher 30-day mortality rate than patients with normal CRP and troponin concentrations (7% vs. 2%, p < 0.01). The CTT test result was an independent predictor for overall mortality even after adjusting for age, sex, and comorbidities (HR = 2.28 [95% CI 1.56-3.37], p < 0.01 for patients with high troponin and high CRP levels). CONCLUSIONS: Early serial CTT results may stratify mortality risk in patients with NSTEMI, especially those with "normal" CRP levels. The CTT could potentially assess the impact of inflammation during myocardial necrosis on the outcomes of patients with NSTEMI and identify patients who could benefit from novel anti-inflammatory therapies.

Relationship among sleep, work features, and SARS-cov-2 vaccine antibody response in hospital workers.

STUDY OBJECTIVES: Immunity is influenced by sleep and the circadian rhythm. Healthcare workers are predisposed to both insufficient sleep and circadian disruption. This study aimed to evaluate the relationship between sleep and work characteristics and the antibody response to the mRNA SARS-CoV-2 vaccine BNT162b2. METHODS: The authors' prospective cohort study ("COVI3") evaluated the effect of a third (booster) dose of the BNT162b2 vaccine. A subset of participants provided information on anthropometric measures, sleep, stress and work characteristics including shift work and number of work hours per week. Blood samples for anti-S1-RBD IgG antibody levels were obtained 21 weeks following receipt of the third dose of the vaccine. RESULTS: In total, 201 healthcare workers (73% women) were included. After adjustment for age, body mass index (BMI), shift work, smoking status, and perceived stress, short sleep duration (<7 h per night) was associated with lower anti-S1-RBD IgG levels (Odds ratio 2.36 [95% confidence interval 1.08-5.13]). Participants who performed shift work had higher odds of lower anti-S1-RBD IgG levels compared to those who did not work in shifts [odds ratio = 2.99 (95% confidence interval 1.40, 6.39)] after accounting for age, short sleep duration, BMI, smoking status and perceived stress. CONCLUSIONS: Shift work and self-reported short sleep duration were associated with a lower antibody response following a booster dose of the SARS-CoV-2 vaccine. These findings suggest that the efficacy of vaccination, particularly among healthcare workers, may be augmented by addressing both sleep and circadian alignment.

Early signaling of inflammation in patients following traumatic injury with accurately estimated time of injury by profiling C-reactive protein levels.

BACKGROUND: Despite its widespread use, the precise dynamics of CRP response in clinical practice remain poorly defined. We employed a novel quadratic model to explore the time-course analysis of CRP values in trauma patients with known precise time of injury. METHODS: Relevant data on all adult patients admitted to our hospital following traumatic incidents between January 1st 2010 to December 31, 2020 were retrospectively collected. Those with a documented time of injury and who underwent CRP evaluation within the first 24 h since injury were studied. RESULTS: Based on the findings from our annual health check-up center, we established a reference upper normal CRP value of 12.99 mg/L. Within the first 7 h after injury, the CRP levels of 8-9% of the 1545 study patients exceeded the reference threshold. The proportion of patients with CRP levels > 12.99 mg/L increased to 18.5% at 8-9 h later and rose sharply to 91.6% at 22-24 h later. Our quadratic model yielded the equation: CRP = 5.122-0.528xTime + 0.139xTime 2. It accounted for > 40% of the variance in CRP levels (R2 = 42.4%). CONCLUSIONS: Clear and prominent CRP elevations following atraumatic event are detected only 9-12 h following the insult. This novel finding has crucial implications for accurate CRP assessment of inflammatory responses to physical injuries.

Transitioning from having no metabolic abnormality nor obesity to metabolic impairment in a cohort of apparently healthy adults.

INTRODUCTION: The global prevalence of metabolic syndrome and its association with increased morbidity and mortality has been rigorously studied. However, the true prevalence of "metabolic health", i.e. individuals without any metabolic abnormalities is not clear. Here, we sought to determine the prevalence of "metabolically healthy" individuals and characterize the "transition phase" from metabolic health to development of dysfunction over a follow-up period of 5 years. METHODS: We included 20,507 individuals from the Tel Aviv Sourasky Medical Center Inflammation Survey (TAMCIS) which comprises apparently healthy individuals attending their annual health survey. A second follow-up visit was documented after 4.8 (± 0.6) years. We defined a group of metabolically healthy participants without metabolic abnormalities nor obesity and compared their characteristics and change in biomarkers over time to participants who developed metabolic impairment on their follow-up visit. The intersections of all metabolic syndrome components and elevated high sensitivity C-reactive protein (hs-CRP) were also analyzed. RESULTS: A quarter of the cohort (5379 individuals, (26.2%) did not fulfill any metabolic syndrome criteria during their baseline visit. A total of 985 individuals (12.7% of returning participants) developed metabolic criteria over time with hypertension being the most prevalent component to develop among these participants. Individuals that became metabolically impaired over time demonstrated increased overlap between metabolic syndrome criteria and elevated hs-CRP levels. The group that became metabolically impaired over time also presented higher delta values of WBC, RBC, liver biomarkers, and uric acid compared with participants who were consistently metabolically impaired. LDL-C (low-density lipoprotein cholesterol) delta levels were similar. CONCLUSIONS: Roughly one-quarter of apparently healthy adults are defined as "metabolically healthy" according to current definitions. The transition from health to metabolic dysfunction is accompanied with active inflammation and several non-metabolic syndrome biomarkers. Aggressive screening for these biomarkers, blood pressure and hs-CRP might help identify apparently healthy individuals at increased risk of developing metabolic syndrome over time.

Comparative analysis of CRP as a biomarker of the inflammatory response intensity among common viral infections affecting the lungs: COVID-19 versus influenza A, influenza B and respiratory syncytial virus.

Severe acute respiratory syndrome-corona virus 2 (SARS-CoV-2) is associated with significant morbidity and mortality. C-reactive protein (CRP) is a useful inflammatory biomarker for patients admitted with an infection. This study aimed to compare CRP level as an indicator of inflammation severity between SARS-CoV-2 and common respiratory viral infections. A cross-sectional study of all adult patients hospitalized in the internal medicine department, geriatric department, or internal intensive care unit between 02/2012 and 06/2021 with laboratory-confirmed respiratory viral infection was performed. SARS-CoV-2, influenza A, influenza B, and respiratory syncytial virus (RSV) were studied. Patients with laboratory-confirmed concurrent viral or bacterial infections were excluded. Patients with malignancy were also excluded. Age, gender, comorbidities, and CRP level upon admission were compared between groups. Univariate and multivariable analyses were applied. Among 1124 patients, 18.2% had SARS­CoV­2, 48.3% influenza A, 18.9% RSV, and 14.6% influenza B. SARS­CoV­2 patients were significantly younger (median 69.4 vs. ≥ 76 years) and had lower Charlson score (median 3 vs. ≥ 4 in other groups) compared to patients with other viral pathogens. After adjustment for patients' age, gender and comorbidities, SARS­CoV­2 patients had a higher probability (OR = 1.84-2.02, p < 0.01) of having CRP values in the upper quartile (> 117 mg/L) compared to all other viral pathogens while between all others there was no significant difference. To conclude, a higher CRP level upon admission is approximately twice more common among SARS-CoV-2 patients compared to other widespread respiratory viruses which may demonstrate the higher intensity of inflammation caused by SARS-CoV-2.

Cholinergic Dysfunction in Patients with Psoriatic Arthritis and Immunocompetent Controls: A Cross-Sectional Study.

BACKGROUND: The parasympathetic system and its main neurotransmitter, acetylcholine, contributes to homeostasis of inflammation. Cholinergic dysregulation is thought to contribute to the pathogenesis of inflammatory rheumatic diseases. Cholinesterase activity in patients with psoriatic arthritis (PsA) has not been investigated. OBJECTIVES: To compare the cholinesterase activity in patients with PsA and immunocompetent controls and to explore the correlation between cholinergic status (CS) and PsA disease activity. METHODS: Serum acetylcholinesterase (AChE) and total cholinesterase activity were measured in patients with PsA (n=88) and matched controls (n=84). Cholinergic activity before and 3-6 months after the initiation of a biologic treatment was evaluated in seven patients with PsA. RESULTS: The levels of AChE and CS were similar in both PsA patients and controls. PsA patients treated with biologics had significantly lower levels of AChE and CS compared to patients treated with non-biologics: 447.4 vs. 526 substrate hydrolyzed/min/ml, P = 0.005, and 1360.9 vs. 1536, P = 0.029, respectively. We found an association between C-reactive protein levels, AChE activity (r = 0.291, P = 0.008), and cholinergic status (r = 0.247, P = 0.026) in patients with PsA but not in controls. No correlation between AChE activity, cholinergic status, and the indices of PsA disease activity was found. After initiating or switching biologic treatment in 7 patients, AChE levels remained stable. CONCLUSIONS: We demonstrated similar cholinesterase activity in patients with psoriatic arthritis and controls, highlighting a potential effect of biologic treatment on cholinergic activity in patients with PsA.

Early signaling of bacteremia in patients who present to the department of emergency medicine with relatively low C-reactive protein (CRP) concentrations.

OBJECTIVES: Examiningthe usefulness of C-reactive protein velocity (CRPv) as an early biomarker for the presence of bacteraemia in patients presenting to the Department of Emergency Medicine with acute infection/inflammation and suspected bacteraemia. METHODS: A retrospective study examining a cohort of patients who presented to the E.R and in whom blood cultures were taken. CRPv was calculated as the difference in mg/hour/litter between two consecutive CRP tests performed within 12 h. RESULTS: 256 patients were included in the cohort. Using CRPv in patients who at first presented with a relatively low (17.9 ≤ mg/L 1stquartile) CRP concentration, we found an AUC of 0.808 ± 0.038 (p < 0.001) for the presence of positive versus negative blood cultures (what is AUC?). This was better than the AUC that was obtained when the WBC for the same purpose. CONCLUSIONS: CRPv may be a useful biomarker in the identification of patients with suspected bacteremiaand a low CRP-a challenging situation for clinicians who may underestimate the severity of illness in this patient group.

Risk of Aseptic Revision and Periprosthetic Fracture Following Bipolar Versus Unipolar Hemiarthroplasty.

Hemiarthroplasty is currently the most common treatment for displaced femoral neck fractures in the elderly. While bipolar hemiarthroplasty was developed to reduce the risk of acetabular erosion that is associated with traditional unipolar hemiarthroplasty, meta-analyses have reported similar outcomes for bipolar and unipolar hemiarthroplasty devices. The primary objective of this study was to evaluate the risks of aseptic revision and periprosthetic fracture following bipolar versus unipolar hemiarthroplasty in a large integrated health-care system in the United States. Methods: We conducted a retrospective cohort study using data from the hip fracture registry of an integrated health-care system. Patients aged ≥60 years who underwent hemiarthroplasty for hip fracture between 2009 and 2019 were included. The primary outcome measure was aseptic revision, and the secondary outcome measure was revision for periprosthetic fracture. Cause-specific Cox proportional hazards regression was performed, with mortality considered as a competing event. In the multivariable analysis, estimates were adjusted for potential confounders such as age, sex, race/ethnicity, body mass index, American Society of Anesthesiologists classification, femoral fixation, surgeon volume, type of anesthesia, and discharge disposition. Results: The study sample included 13,939 patients who had been treated with hemiarthroplasty by 498 surgeons at 35 hospitals. The mean follow-up time was 3.7 ± 2.9 years. The overall incidence of aseptic revision at 5 years following hemiarthroplasty was 2.8% (386). In the multivariable analysis controlling for potential confounders, bipolar hemiarthroplasty was associated with a lower risk of aseptic revision than unipolar hemiarthroplasty (hazard ratio [HR], 0.74; 95% confidence interval [CI], 0.59 to 0.94; p = 0.012). Rates of revision for periprosthetic fracture were similar between the bipolar and unipolar devices (HR, 0.79; 95% CI, 0.58 to 1.10; p = 0.16). Conclusions: In this study of hemiarthroplasty for hip fracture in elderly patients, bipolar designs were associated with a lower risk of aseptic revision than unipolar designs. In contrast to prior research, we did not find any difference in the risk of periprosthetic fracture between the 2 designs. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Metabolically Healthy Obesity Is a Misnomer: Components of the Metabolic Syndrome Linearly Increase with BMI as a Function of Age and Gender.

OBJECTIVES: We aimed to examine the relationships between body mass index (BMI) and metabolic syndrome (MS) components as a function of age and gender across weight categories. METHODS: This cross-sectional study included 19,328 subjects who participated in a health-screening program. We analyzed 14,093 apparently healthy subjects with a BMI ≥ 18.5 kg/m2 (ranging from 18.5 to 46 kg/m2). RESULTS: At a BMI of 18.5 kg/m2, 16% of subjects had one or more MS components (MS ≥ 1). The number of MS components increased linearly with BMI. The most prevalent components for MS1-4 were hypertension (in men) and increased waist circumference (in women). Among 6391 non-obese subjects with MS = 0, there was a linear increase in blood pressure, glucose, and triglycerides, as well as a decline in high-density lipoprotein cholesterol, as BMI increased. In 2087 subjects with a BMI ≥ 30 kg/m2, a true normometabolic state (MS = 0) was observed in only 7.5%, declining to less than 1% at a BMI ≥ 36 kg/m2 (ATP criteria). Women were metabolically protected relative to men between the ages of 30 and 50 years. CONCLUSIONS: (A) MS components increase linearly with BMI from the lowest normal BMI and continue to increase with age and BMI; (B) metabolically healthy obesity is rare in subjects with a high BMI and declines with age; (C) hypertension is the most common component in men; and (D) in women, MS components are seen at older ages than in men for the same BMI. Metabolic health declines with age and BMI in nearly all subjects with obesity.

The effect of body mass index reduction on intraocular pressure in a large prospective cohort of apparently healthy individuals in Israel.

PURPOSE: To investigate the effect of change in body mass index (BMI) on intraocular pressure (IOP) in a large cohort of apparently healthy volunteers who underwent an annual comprehensive screening examinations. METHODS: This study included individuals who were enrolled in the Tel Aviv Medical Center Inflammation Survey (TAMCIS) and had IOP and BMI measurements at their baseline and follow up visits. Relationships between BMI and IOP and the effect of change in BMI on IOP were investigated. RESULTS: A total of 7,782 individuals had at least one IOP measurement at their baseline visit, and 2,985 individuals had ≥2 visits recorded. The mean (SD) IOP (right eye) was 14.6 (2.5) mm Hg and mean (SD) BMI was 26.4 (4.1) kg/m2. IOP positively correlated with BMI levels (r = 0.16, p<0.0001). For individuals with morbid obesity (BMI≥35 kg/m2) and ≥2 visits, a change in BMI between the baseline and first follow-up visits correlated positively with a change in the IOP (r = 0.23, p = 0.029). Subgroup analysis of subjects who had a reduction of at least 2 BMI units showed a stronger positive correlation between change in BMI and change in IOP (r = 0.29, p<0.0001). For this subgroup, a reduction of 2.86 kg/m2 of BMI was associated with a reduction of 1 mm Hg in IOP. CONCLUSIONS: BMI loss correlated with reduction in IOP, and this correlation was more pronounced among morbidly obese individuals.

Sex- and ethnic-specific patterns in the incidence of hip fracture among older US Asian and non-Hispanic White adults.

BACKGROUND: Asian and Pacific Islander (Asian/PI) adults have lower hip fracture incidence than non-Hispanic White (NHW) adults, but data regarding Asian/PI subgroups are limited. We compared hip fracture incidence among older US Asian/PI and NHW populations, including ethnic subgroup differences. METHODS: Using observational data from a California healthcare system, we identified Asian/PI and NHW adults aged ≥50 years (2000-2019) and followed subjects to 2021 for hip fracture determined by principal/primary hospital diagnosis or by secondary hospital diagnosis with hip/femur procedure codes. Age-adjusted hip fracture incidence was calculated with 95% confidence intervals (CIs). Log-Poisson regression was used to determine fracture incidence rate ratios (IRRs, [CI]; NHW or Chinese as reference) adjusting for age and year. RESULTS: Among 215,359 Asian/PI and 776,839 NHW women, hip fracture incidence was 1.34 (1.28-1.40) and 2.97 (2.94-3.01) per 1000 person-years, respectively, with IRR 0.45 (0.43-0.47). Among 188,328 Asian/PI and 697,046 NHW men, hip fracture incidence was 0.62 (0.58-0.67) and 1.81 (1.78-1.84) per 1000 person-years, respectively, with IRR 0.34 (0.32-0.37). For the four largest Asian/PI subgroups, Filipina women (IRR 0.85 [0.75-0.96]) had lower, and Japanese (IRR 1.36 [1.20-1.54]) and South Asian (IRR 1.36 [1.07-1.72]) women had higher hip fracture incidence compared to Chinese women. Hip fracture incidence was only higher among South Asian (IRR 1.61 [1.21-2.14]) compared to Chinese men. CONCLUSION: Hip fracture incidence among US Asian/PI adults was 55% (women) and 66% (men) lower than NHW adults, but incidence varied by Asian/PI subgroup. The heterogeneity among Asian/PI adults highlights the importance of examining fracture risk by ethnic subgroup.

Association of inflammatory markers with hearing loss in young adults.

OBJECTIVES: To assess the correlation between inflammatory markers (IM) and hearing loss (HL) in a large cohort of apparently healthy individuals. DESIGN: A cross sectional study. SETTING: Tel-Aviv Medical Center (a tertiary referral center) Inflammatory Survey Participants Individuals who attended the Tel-Aviv Medical Center Inflammatory Survey (TAMCIS) for a routine annual health check. RESULTS: Out of 2,500 individuals included in the final study cohort, 1,170 (47.3%) had some hearing impairment. Those with a hearing loss in 1 or both ears had significantly higher levels of neutrophils, lymphocytes, neutrophil-to-lymphocyte ratio, monocyte-to-lymphocyte ratio, and red blood cell counts. There was a difference between low- and high- frequencies losses associated with the inflammatory status. CONCLUSIONS: IM levels were associated with the presence of a HL, supporting a link between inflammatory changes and hearing loss.

Differentiating between bacterial and viral infections by estimated CRP velocity.

PURPOSE: Differentiating between acute viral and bacterial infection is challenging due to the similarity in symptom presentation. Blood tests can assist in the diagnosis, but they reflect the immediate status and fail to consider the dynamics of an inflammatory response with time since symptom onset. We applied estimated C-reactive protein (CRP) velocity (eCRPv), as derived from the admission CRP level divided by time from symptom onset, in order to better distinguish between viral and bacterial infections. METHODS: This cross-sectional study included patients admitted to the emergency department with a confirmed viral (n = 83) or bacterial (n = 181) infection. eCRPv was defined as the ratio between the absolute CRP level upon admission to time from symptom onset (in hours). Absolute CRP and eCRPv values were compared between the 3 groups. RESULTS: Bacterial patients presented with higher CRP levels (133 mg/L) upon admission compared to viral patients (23.31 mg/L) (P < 0.001). Their median value of eCRPv velocity was 4 times higher compared to the viral patients (1.1 mg/L/h compared 0.25 mg/L/h, P < 0.001). Moreover, in intermediate values of CRP (100-150 mg/L) upon admission, in which the differential diagnosis is controversial, high eCRPv is indicative of bacterial infection, eCRPv >4 mg/L/h represents only bacterial patients. CONCLUSIONS: During an acute febrile illness, the eCRPv value can be used for rapid differentiation between bacterial and viral infection, especially in patients with high CRP values. This capability can potentially expedite the provision of appropriate therapeutic management. Further research and validation may open new applications of the kinetics of inflammation for rapid diagnosis of an infectious vs. a viral source of fever.

Sepsis Related Mortality Associated with an Inflammatory Burst in Patients Admitting to the Department of Internal Medicine with Apparently Normal C-Reactive Protein Concentration.

Background: Patients who are admitted to the Department of Internal Medicine with apparently normal C-reactive protein (CRP) concentration impose a special challenge due the assumption that they might not harbor a severe and potentially lethal medical condition. Methods: A retrospective cohort of all patients who were admitted to the Department of Internal Medicine with a CRP concentration of ≤31.9 mg/L and had a second CRP test obtained within the next 24 h. Seven day mortality data were analyzed. Results: Overall, 3504 patients were analyzed with a mean first and second CRP of 8.8 (8.5) and 14.6 (21.6) mg/L, respectively. The seven day mortality increased from 1.8% in the first quartile of the first CRP to 7.5% in the fourth quartile of the first CRP (p < 0.0001) and from 0.6% in the first quartile of the second CRP to 9.5% in the fourth quartile of the second CRP test (p < 0.0001), suggesting a clear relation between the admission CRP and in hospital seven day mortality. Conclusions: An association exists between the quartiles of CRP and 7-day mortality as well as sepsis related cause of death. Furthermore, the CRP values 24 h after hospital admission improved the discrimination.

Short-Term Safety of Booster Immunization With BNT162b2 mRNA COVID-19 Vaccine in Healthcare Workers.

This study demonstrated a favorable short-term safety profile after a third dose of the BNT162b2 vaccine among healthcare workers (HCWs). There were more frequent local reactions and less systemic reactions compared to the second dose. The HCWs who reported reactions had higher prebooster titer of anti-S1 antibodies compared to those who reported no reactions.

Stratifying individuals into non-alcoholic fatty liver disease risk levels using time series machine learning models.

Non-alcoholic fatty liver disease (NAFLD) affects 25% of the population worldwide, and its prevalence is anticipated to increase globally. While most NAFLD patients are asymptomatic, NAFLD may progress to fibrosis, cirrhosis, cardiovascular disease, and diabetes. Research reports, with daunting results, show the challenge that NAFLD's burden causes to global population health. The current process for identifying fibrosis risk levels is inefficient, expensive, does not cover all potential populations, and does not identify the risk in time. Instead of invasive liver biopsies, we implemented a non-invasive fibrosis assessment process calculated from clinical data (accessed via EMRs/EHRs). We stratified patients' risks for fibrosis from 2007 to 2017 by modeling the risk in 5579 individuals. The process involved time-series machine learning models (Hidden Markov Models and Group-Based Trajectory Models) profiled fibrosis risk by modeling patients' latent medical status resulted in three groups. The high-risk group had abnormal lab test values and a higher prevalence of chronic conditions. This study can help overcome the inefficient, traditional process of detecting fibrosis via biopsies (that are also medically unfeasible due to their invasive nature, the medical resources involved, and costs) at early stages. Thus longitudinal risk assessment may be used to make population-specific medical recommendations targeting early detection of high risk patients, to avoid the development of fibrosis disease and its complications as well as decrease healthcare costs.

Association of a Third Dose of BNT162b2 Vaccine With Incidence of SARS-CoV-2 Infection Among Health Care Workers in Israel.

Importance: Administration of a BNT162b2 booster dose (Pfizer-BioNTech) to fully vaccinated individuals aged 60 years and older was significantly associated with lower risk of SARS-CoV-2 infection and severe illness. Data are lacking on the effectiveness of booster doses for younger individuals and health care workers. Objective: To estimate the association of a BNT162b2 booster dose with SARS-CoV-2 infections among health care workers who were previously vaccinated with a 2-dose series of BNT162b2. Design, Setting, and Participants: This was a prospective cohort study conducted at a tertiary medical center in Tel Aviv, Israel. The study cohort included 1928 immunocompetent health care workers who were previously vaccinated with a 2-dose series of BNT162b2, and had enrolled between August 8 and 19, 2021, with final follow-up reported through September 20, 2021. Screening for SARS-CoV-2 infection was performed every 14 days. Anti-spike protein receptor binding domain IgG titers were determined at baseline and 1 month after enrollment. Cox regression with time-dependent analysis was used to estimate hazard ratios of SARS-CoV-2 infection between booster-immunized status and 2-dose vaccinated (booster-nonimmunized) status. Exposures: Vaccination with a booster dose of BNT162b2 vaccine. Main Outcomes and Measures: The primary outcome was SARS-CoV-2 infection, as confirmed by reverse transcriptase-polymerase chain reaction. Results: Among 1928 participants, the median age was 44 years (IQR, 36-52 years) and 1381 were women (71.6%). Participants completed the 2-dose vaccination series a median of 210 days (IQR, 205-213 days) before study enrollment. A total of 1650 participants (85.6%) received the booster dose. During a median follow-up of 39 days (IQR, 35-41 days), SARS-CoV-2 infection occurred in 44 participants (incidence rate, 60.2 per 100 000 person-days); 31 (70.5%) were symptomatic. Five SARS-CoV-2 infections occurred in booster-immunized participants and 39 in booster-nonimmunized participants (incidence rate, 12.8 vs 116 per 100 000 person-days, respectively). In a time-dependent Cox regression analysis, the adjusted hazard ratio of SARS-CoV-2 infection for booster-immunized vs booster-nonimmunized participants was 0.07 (95% CI, 0.02-0.20). Conclusions and Relevance: Among health care workers at a single center in Israel who were previously vaccinated with a 2-dose series of BNT162b2, administration of a booster dose compared with not receiving one was associated with a significantly lower rate of SARS-CoV-2 infection over a median of 39 days of follow-up. Ongoing surveillance is required to assess durability of the findings.