Expanding optimization ensemble model methods for forecasting seasonal influenza in the U.S.
Bibliographic record
Abstract
ABSTRACT Each year, the seasonal influenza epidemic sees significant variability in its evolution. Accurate forecasts of future influenza cases are important for planning public health responses. The United States Centers for Disease Control and Prevention (CDC) has annually organized the FluSight competition ( https://github.com/cdcepi/FluSight-forecast-hub ) to solicit forecasts from participating teams over horizons of 1, 2, and 3 weeks ahead. Using these data, the CDC produces an ensemble forecast of all submitted forecasts. In this paper, we introduce a new weight-based ensemble forecasting method to consider predicting laboratory-confirmed influenza hospital admissions for the 2024-2025 season. The method consists of determining optimal weights that are updated week-by-week throughout the FluSight competition to minimize the mean squared error (MSE) of a blend of teams’ previous forecasts compared to the truth data. Using these weights over an expanding time window starting at the beginning of the season (late Fall), we produce our own future forecasts; we call our method the expanding window optimization ensemble (EWO). To improve our method’s performance vis-a-vis the CDC ensemble model, we further introduce the Adjusted-Weights expanding window optimization ensemble (Adw-EWO) method. This new forecast is obtained by adding a correction term to the original EWO forecast, controlled by a parameter π ∈ (0, 1). We adaptively tune π to enhance forecasting performance of Adw-EWO vis-a-vis the CDC ensemble model. The correction term is computed using only the forecast errors at horizon 0 and is then applied uniformly across all forecast horizons. Our results show that the Adw-EWO method consistently outperforms the EWO across all horizons. Moreover, the Adw-EWO outperforms the CDC ensemble model at horizons 0, 1, and 2, while at horizon 3, the performance of Adw-EWO and the CDC ensemble was roughly comparable.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".