Background: The 2023–2024 US influenza season was characterized by a predominance of A(H1N1)pdm09 virus circulation with cocirculation of A(H3N2) and B/Victoria viruses. We estimated vaccine effectiveness (VE) in the United States against mild-to-moderate medically attended influenza illness in the 2023–2024 season. Methods: We enrolled outpatients aged ≥8 months with acute respiratory illness in 7 states. Respiratory specimens were tested for influenza type/subtype by reverse-transcriptase polymerase chain reaction. Influenza VE was estimated with a test-negative design comparing odds of testing positive for influenza among vaccinated versus unvaccinated participants. We estimated VE by virus subtype/lineage and A(H1N1)pdm09 genetic subclades. Results: Among 6629 enrolled patients, 1780 (27%) tested positive for influenza, including 806 with A(H1N1)pdm09, 567 with B/Victoria, and 328 with A(H3N2). VE against any influenza illness was 44% (95% confidence interval, 36%–51%): 29% (15%–41%) against influenza A(H1N1)pdm09, 74% (65%–81%) against B/Victoria, and 30% (8%–47%) against A(H3N2). Statistically significant protection against any influenza was found for all age groups except adults aged 50–64 years. Lack of protection in this age group was specific to influenza A–associated illness. We observed differences in VE by birth cohort and A(H1N1)pdm09 virus genetic subclade. Conclusions: Vaccination reduced outpatient medically attended influenza overall by 44% and provided protection overall against circulating influenza A and B viruses. Serologic studies would help inform differences observed by age groups.

Background: Urinary tract infection (UTI) is a commonly misdiagnosed infectious syndrome. Diagnostic stewardship interventions can reduce rates of asymptomatic bacteriuria treatment but are often labor intensive, and thus an automated means of reducing unnecessary urine testing is preferred. In this systematic review and meta-analysis, we sought to identify studies describing interventions utilizing clinical decision support (CDS) to optimize UTI diagnosis and to characterize the effectiveness of these interventions. Methods: We conducted a comprehensive electronic search and manual reference list review for peer-reviewed articles published before July 2, 2021. Publications describing an intervention intending to enhance UTI diagnosis via CDS were included. The primary outcome was urine culture test rate. Results: The electronic search identified 5013 studies for screening. After screening and full-text review, 9 studies met criteria for inclusion, and a manual reference list review identified 5 additional studies, yielding a total of 14 studies included in the systematic review. The most common CDS intervention was urinalysis with reflex to urine culture based on prespecified urinalysis parameters. All 9 studies that provided statistical comparisons reported a decreased urine culture rate postintervention, 8 of which were statistically significant. A meta-analysis including 4 studies identified a pooled urine culture incidence rate ratio of 0.56 (95% confidence interval, .52–.60) favoring the postintervention versus preintervention group. Conclusions: In this systematic review and meta-analysis, CDS appeared to be effective in decreasing urine culture rates. Prospective trials are needed to confirm these findings and to evaluate their impact on antimicrobial prescribing, patient-relevant outcomes, and potential adverse effects.

Background: The 2022–23 US influenza season peaked early in fall 2022.Methods: Late‐season influenza vaccine effectiveness (VE) against outpatient, laboratory‐confirmed influenza was calculated among participants of the US Influenza VE Network using a test‐negative design.Results: Of 2561 participants enrolled from December 12, 2022 to April 30, 2023, 91 laboratory‐confirmed influenza cases primarily had A(H1N1)pdm09 (6B.1A.5a.2a.1) or A(H3N2) (3C.2a1b.2a.2b). Overall, VE was 30% (95% confidence interval −9%, 54%); low late‐season activity precluded estimation for most subgroups.Conclusions: 2022–23 late‐season outpatient influenza VE was not statistically significant. Genomic characterization may improve the identification of influenza viruses that circulate postinfluenza peak.