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PubMed · 11177840

Search for the decay KL --> pi(0)e+e-.

A Alavi-Harati·I F Albuquerque·T Alexopoulos·M Arenton·K Arisaka·S Averitte·A R Barker·L Bellantoni·A Bellavance·J Belz·R Ben-David·D R Bergman·E Blucher·G J Bock·C Bown·S Bright·E Cheu·S Childress·R Coleman·M D Corcoran·G Corti·B Cox·M B Crisler·A R Erwin·R Ford·P M Fordyce·A Glazov·A Golossanov·G Graham·J Graham·K Hagan·E Halkiadakis·K Hanagaki·S Hidaka·Y B Hsiung·V Jejer·J Jennings·D A Jensen·R Kessler·H G Kobrak·J LaDue·A Lath·A Ledovskoy·P L McBride·A P McManus·P Mikelsons·E Monnier·T Nakaya·K S Nelson·H Nguyen·V O'Dell·M Pang·R Pordes·V Prasad·C Qiao·B Quinn·E J Ramberg·R E Ray·A Roodman·M Sadamoto·S Schnetzer·K Senyo·P Shanahan·P S Shawhan·W Slater·N Solomey·S V Somalwar·R L Stone·I Suzuki·E C Swallow·R A Swanson·S A Taegar·R J Tesarek·G B Thomson·P A Toale·A Tripathi·R Tschirhart·Y W Wah·J Wang·H B White·J Whitmore·B Winstein·R Winston·T Yamanaka·E D Zimmerman
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Abstract

We report on a search for the decay KL-->pi(0)e+e- carried out by the KTeV/E799 experiment at Fermilab. This decay is expected to have a significant CP violating contribution and the measurement of its branching ratio could support the Cabibbo-Kobayashi-Maskawa mechanism for CP violation or could point to new physics. Two events were observed in the 1997 data with an expected background of 1.06+/-0.41 events, and we set an upper limit B(KL-->pi(0)e+e-)<5.1 x 10(-10) at the 90% confidence level.

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A Alavi-Harati, I F Albuquerque, T Alexopoulos, M Arenton, K Arisaka, S Averitte, A R Barker, L Bellantoni, A Bellavance, J Belz, R Ben-David, D R Bergman, E Blucher, G J Bock, C Bown, S Bright, E Cheu, S Childress, R Coleman, M D Corcoran, G Corti, B Cox, M B Crisler, A R Erwin, R Ford, P M Fordyce, A Glazov, A Golossanov, G Graham, J Graham, K Hagan, E Halkiadakis, K Hanagaki, S Hidaka, Y B Hsiung, V Jejer, J Jennings, D A Jensen, R Kessler, H G Kobrak, J LaDue, A Lath, A Ledovskoy, P L McBride, A P McManus, P Mikelsons, E Monnier, T Nakaya, K S Nelson, H Nguyen, V O'Dell, M Pang, R Pordes, V Prasad, C Qiao, B Quinn, E J Ramberg, R E Ray, A Roodman, M Sadamoto, S Schnetzer, K Senyo, P Shanahan, P S Shawhan, W Slater, N Solomey, S V Somalwar, R L Stone, I Suzuki, E C Swallow, R A Swanson, S A Taegar, R J Tesarek, G B Thomson, P A Toale, A Tripathi, R Tschirhart, Y W Wah, J Wang, H B White, J Whitmore, B Winstein, R Winston, T Yamanaka, E D Zimmerman. 2001-01-15. Search for the decay KL --> pi(0)e+e-.. https://doi.org/10.1103/physrevlett.86.397

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Effectiveness of high-dose versus standard-dose influenza vaccines against hospitalisation according to frailty risk: a prespecified analysis of the randomised trial DANFLU-2.

BACKGROUND: Frailty is a major risk factor for influenza-related complications and can influence vaccine effectiveness. We aimed to assess the relative vaccine effectiveness (rVE) of high-dose (HD-IIV) versus standard-dose inactivated influenza vaccine (SD-IIV) in older adults aged 65 years or older according to frailty risk. METHODS: This study was a prespecified analysis of DANFLU-2, an open-label, individually randomised trial, conducted in Denmark during three consecutive influenza seasons (2022-23, 2023-24, and 2024-25). Adults aged 65 years or older were randomised (1:1) to the HD-IIV or SD-IIV group. The primary endpoint was hospitalisation for influenza or pneumonia. Frailty was defined according to the validated Hospital Frailty Risk Score (HFRS) based on ICD-10 codes within 10 years before randomisation. Participants were stratified into three HFRS categories, namely low (<5 points), intermediate (5-15 points), and high (>15 points) frailty risk. The rVE of HD-IIV versus SD-IIV against the primary endpoint was assessed across prespecified HFRS categories and treating HFRS as a continuous variable. Pearson's chi-square test was used to compare safety events across frailty risk groups and randomisation groups. FINDINGS: Among 332&#x2009;438 randomised participants (mean age 73&#xb7;7 years [SD 5&#xb7;8]; 161&#x2009;538 [48&#xb7;6%] were female), 276&#x2009;173 (83&#xb7;1%) had low frailty risk, 52&#x2009;395 (15&#xb7;8%) had intermediate frailty risk, and 3861 (1&#xb7;2%) had high frailty risk. The primary endpoint of hospitalisation for influenza or pneumonia occurred in 1424 (0&#xb7;5%) of 276&#x2009;173 participants with low frailty risk, 761 (1&#xb7;5%) of 52&#x2009;395 with intermediate frailty risk, and 163 (4&#xb7;2%) of 3861 with high frailty risk (relative risk [RR] for intermediate vs low frailty risk 2&#xb7;8 [95% CI 2&#xb7;6-3&#xb7;1]; RR for high vs low frailty risk 8&#xb7;2 [7&#xb7;0-9&#xb7;6]). HFRS as a continuous variable significantly modified the effect of HD-IIV versus SD-IIV against the primary endpoint with higher rVE estimates with increasing HFRS (pinteraction=0&#xb7;020). The rVE was 0&#xb7;2% (95% CI -10&#xb7;8 to 10&#xb7;2) among those with low frailty risk, 13&#xb7;1% (-0&#xb7;4 to 24&#xb7;8) among those with intermediate frailty risk, and 19&#xb7;9% (-10&#xb7;3 to 42&#xb7;1) among those with high frailty risk. No significant interaction was observed when HFRS was assessed according to the prespecified categorical frailty groups (pinteraction=0&#xb7;17). The proportion of participants with at least one serious adverse event increased across frailty risk groups (13&#x2009;366 [4&#xb7;8%] of 275&#x2009;795 for low frailty risk, 5475 [10&#xb7;5%] of 52&#x2009;315 for intermediate frailty risk, and 777 [20&#xb7;2%] of 3850 for high frailty risk; p<0&#xb7;0001), with similar proportions of serious adverse events in the HD-IIV and SD-IIV groups for each frailty risk group. INTERPRETATION: Among adults aged 65 years or older in Denmark, frailty risk might modify the effects of HD-IIV versus SD-IIV against hospitalisation for influenza or pneumonia, with higher rVE estimates with increasing frailty risk. These findings might support considering high-dose influenza vaccines for frail older adults. However, effect modification was not evident when frailty was assessed using prespecified categorical subgroups, and subgroup-specific estimates were imprecise, with 95% CIs crossing the null. These results should be considered exploratory, warranting further investigation. FUNDING: The DANFLU-2 trial was funded by Sanofi.

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