Evaluation of FluSight Influenza Forecasting in the 2021-22 and 2022-23 Seasons with a New Target Laboratory-Confirmed Influenza Hospitalizations

Accurate forecasts can enable more effective public health responses during seasonal influenza epidemics. Forecasting teams were asked to provide national and jurisdiction-specific probabilistic predictions of weekly confirmed influenza hospital admissions for one through four weeks ahead for the 2021-22 and 2022-23 influenza seasons. Across both seasons, 26 teams submitted forecasts, with the submitting teams varying between seasons. Forecast skill was evaluated using the Weighted Interval Score (WIS), relative WIS, and coverage. Six out of 23 models outperformed the baseline model across forecast weeks and locations in 2021-22 and 12 out of 18 models in 2022-23. Averaging across all forecast targets, the FluSight ensemble was the 2nd most accurate model measured by WIS in 2021-22 and the 5th most accurate in the 2022-23 season. Forecast skill and 95% coverage for the FluSight ensemble and most component models degraded over longer forecast horizons and during periods of rapid change. Current influenza forecasting efforts help inform situational awareness, but research is needed to address limitations, including decreased performance during periods of changing epidemic dynamics. ### Competing Interest Statement E.W.T. is an employee of Sanofi, which manufactures influenza vaccines. J.S. and Columbia University disclose partial ownership of SK Analytics. J.S. discloses consulting for BNI. ### Funding Statement M.B.N., P.R., J.T., S.V., A.A., G.K., B.H., B.L.L., M.V.M., M.A.A, A.S. disclose support for the research of this work from the Centers for Disease Control and Prevention (CDC) and Council of State and Territorial Epidemiologists (CSTE), [Cooperative Agreement number NU380T000297] M.C., J.D, K.M., X.X, APP, AV, P.C.V., A.G.K. M.L., M.A. disclose support for the research of this work from the HHS/CDC 6U01IP001137 and HHS/CDC 5U01IP0001137. B.A.P., A.R., H.P.K., Z.Z., G.G., P.A., S.S.B., R.V.V., disclose support for the research of this work from NSF (Expeditions CCF-1918770, CAREER IIS-2028586, RAPID IIS-2027862, Medium IIS-1955883, Medium IIS-2106961, PIPP CCF-2200269), CDC MInD program, faculty gifts from Facebook/Meta, and funds/computing resources from Georgia Tech and GTRI. M.S., L.C. F.L and A.G. M. disclose support for the research of this work from the Centers for Disease Control and Prevention (CDC) and Council of State and Territorial Epidemiologists (CSTE), [Cooperative Agreement number NU380T000297] M.S. discloses support for the research of this work from the National Institutes of Health (grant number R01GM130668) and (in part) by contract 200-2016-91779 with the Centers for Disease Control and Prevention. S.V., A.A., G.K., B.H., B.L.L., M.V.M., also disclose support for the research of this work from NSF Expeditions CCF-1918656, VDH Grant VDH-21-501-0135, University of Virginia Strategic Investment Fund Award SIF160. L.C.B., A.G., A.J.H., D.J.M., R.R., D.S., R.J.T. disclose support for the research of this work from the Centers for Disease Control and Prevention U011P001121 and Centers for Disease Control and Prevention 75D30123C15907. B.T.S., S.A.S., H.L.G., and P.B. disclose support for the research of this work from the Centers for Disease Control and Prevention (CDC) and Council of State and Territorial Epidemiologists (CSTE), [Cooperative Agreement number NU38OT000297] N.R. discloses support from National Science Foundation grants CCF-1918770, NRT DGE-1545362, and OAC-1835660. S.T., C.P.S., A.H. disclose support for the research of this work from the National Science Foundation [2127976]. S.T., C.P.S., A.H., J.L., J.C.L., S.L.L., C.D.M., K.S., S-m.J. disclose support from the Centers for Disease Control and Prevention [200-2016-91781]. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced are available online at