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Background Risk of infection with SARS-CoV-2 has remained high among health care personnel (HCP) throughout the pandemic, due to both exposure in the community and occupational settings. While vaccine uptake among health care workers is high, real-world continual monitoring of vaccine effectiveness (VE) among this population is crucial for informing future vaccination and prevention efforts. Methods Data for this analysis came from a test-negative case-control study conducted among HCP working at two acute care hospitals in Monroe County, NY from December 2020 through March 2022, performed as part of the CDC Emerging Infections Program. Case participants were identified as HCP who had at least one COVID-19 like symptom, and a positive polymerase-chain-reaction (PCR) SARS-CoV-2 test during the study time period. Control participants had a negative SARS-CoV-2 PCR test, regardless of presence of COVID-19 like symptoms. Cases and controls were matched based on the study week of their test date. Conditional logistic regression was used to assess vaccine effectiveness against symptomatic infection. Effectiveness was assessed between December 2020-May 2021, May 2021-October 2021, and October 2021-March 2022. Results From December 28th, 2020 through March 12th, 2022, 881 cases and 1794 controls were enrolled. Vaccine effectiveness against symptomatic infection was greatest from December 2020 through May 2021, with mRNA complete series effectiveness at 93.1% (95% CI: 86.9%-96.3%) with complete series VE falling to 25.1% (95% CI: 0.0%-50.9%) during May 2021-October 2021. Waning immunity following receipt of second dose was observed across all time periods. Vaccine effectiveness following receipt of one booster vaccine was found to be 59.2% (95% CI: 43.5-70.6), with evidence of waning immunity two months from receipt of the booster (VE: 46.6%; 95% CI: 14.6%-66.7%). Conclusion Protection provided by the COVID-19 mRNA vaccines against symptomatic infection is highly variable among HCP, based on the circulating dominant variant and the time since receipt of each dose. Monitoring of vaccine effectiveness, as well as waning immunity, among this high-risk population is essential to guide future vaccine policies. Disclosures christopher J. Myers, MS, Infectious diseases, Pfizer: Grant/Research Support Ghinwa Dumyati, MD, Pfizer: Grant/Research Support.

Background An increasing proportion of Clostridium difficile infections (CDI) in the United States are community-associated (CA). We conducted a case-control study to identify CA-CDI risk factors. Methods We enrolled participants from 10 US sites during October 2014–March 2015. Case patients were defined as persons age ≥18 years with a positive C. difficile specimen collected as an outpatient or within 3 days of hospitalization who had no admission to a health care facility in the prior 12 weeks and no prior CDI diagnosis. Each case patient was matched to one control (persons without CDI). Participants were interviewed about relevant exposures; multivariate conditional logistic regression was performed. Results Of 226 pairs, 70.4% were female and 52.2% were ≥60 years old. More case patients than controls had prior outpatient health care (82.1% vs 57.9%; P < .0001) and antibiotic (62.2% vs 10.3%; P < .0001) exposures. In multivariate analysis, antibiotic exposure—that is, cephalosporin (adjusted matched odds ratio [AmOR], 19.02; 95% CI, 1.13–321.39), clindamycin (AmOR, 35.31; 95% CI, 4.01–311.14), fluoroquinolone (AmOR, 30.71; 95% CI, 2.77–340.05) and beta-lactam and/or beta-lactamase inhibitor combination (AmOR, 9.87; 95% CI, 2.76–340.05),—emergency department visit (AmOR, 17.37; 95% CI, 1.99–151.22), white race (AmOR 7.67; 95% CI, 2.34–25.20), cardiac disease (AmOR, 4.87; 95% CI, 1.20–19.80), chronic kidney disease (AmOR, 12.12; 95% CI, 1.24–118.89), and inflammatory bowel disease (AmOR, 5.13; 95% CI, 1.27–20.79) were associated with CA-CDI. Conclusions Antibiotics remain an important risk factor for CA-CDI, underscoring the importance of appropriate outpatient prescribing. Emergency departments might be an environmental source of CDI; further investigation of their contribution to CDI transmission is needed.

Background Carbapenem-resistant Enterobacteriaceae (CRE) are an urgent threat in the United States because of high morbidity and mortality, few treatment options, and potential for rapid spread among patients. To assess for changes in CRE epidemiology and risk among populations, we analyzed CDC Emerging Infections Program (EIP) 2012–2015 surveillance data for CRE. Methods Active, population-based CRE surveillance was initiated in January 2012 at 3 EIP sites (GA, MN, OR) and expanded to 5 additional sites (CO, MD, NM, New York, TN) by 2014. An incident case was the first Escherichia coli, Enterobacter, or Klebsiella isolate (non-susceptible to at least one carbapenem and resistant to all third-generation cephalosporins tested) collected from urine or a normally sterile body site from a patient during a 30-day period. Data were collected from patients’ medical records. Cases were hospital-onset (HO) or long-term care facility (LTCF) onset if patients were in the respective facility ≥3 days prior to culture or at the time of culture; and community-onset (CO) otherwise. We calculated incidence rates based on census data for EIP sites and described by type of infection onset. Results A total of 1,582 incident CRE cases were reported in 2012–2015. Most cases (88%) were identified through urine cultures; 946 (60%) were female, and median age was 66 years (interquartile range: 55–77). The median incidence by site was 2.95 per 100,000 population (range: 0.35–8.98). Among the three sites with four full years of data, a different trend was seen in each (Figure). Trends in GA and MN were statistically significant, and no significant trend was seen in OR. Overall, 480 cases (30%) were HO, 524 (33%) were LTCF onset, and 578 (37%) were CO. Of CO cases, 308 (53%) had been hospitalized, admitted to a long- term acute care hospital or were a LTCF resident in the prior year. Conclusion CRE incidence varied more than 20-fold across surveillance sites, with evidence of continued increases in MN. Measuring impact of programs aimed at reducing CRE transmission in other regions will require obtaining local data to identify cases occurring during and after healthcare facility discharge. Further study of changes in incidence in some settings and areas might offer opportunities to refine and expand effective control strategies. Disclosures All authors: No reported disclosures.