For the past two years, the COVID-19 pandemic has exerted pressure on the hospital system, with consequences for patients' care pathways. To support hospital planning strategies, it is important to anticipate COVID-19 health care demand and to continue to improve predictive models.
In this study published in the journal PNAS, scientists from the Mathematical Modeling of Infectious Diseases Unit at the Institut Pasteur identified the most relevant predictive variables for anticipating hospital demand and proposed using an ensemble model based on the average of the predictions of several individual models.
The scientists began by evaluating the performance of 12 individual models and 19 predictive variables, or "predictors," such as epidemiological data (for example the number of cases) and meteorological or mobility data (for example the use of public transport). The scientists showed that the models incorporating these early predictive variables performed better. The average prediction error was halved for 14-day-ahead predictions. "These early variables detect changes in epidemic dynamics more quickly," explains Simon Cauchemez, Head of the Mathematical Modeling of Infectious Diseases Unit at the Institut Pasteur and last author of the study. "The models that performed best used at least one epidemiological predictor and one mobility predictor," he continues. The addition of a meteorological variable also improved forecasts but with a more limited impact.
The scientists then built an ensemble model, taking the average of several individual models, and tested the model retrospectively using epidemiological data from March to July 2021. This approach is already used in climate forecasting. "Our study shows that it is preferable to develop an ensemble model, as this reduces the risk of the predicted trajectory being overly influenced by the assumptions of a specific model," explains Juliette Paireau, a research engineer in the Mathematical Modeling of Infectious Diseases Unit at the Institut Pasteur and joint first author of the study.
This ensemble model has been used to monitor the epidemic in France since January 15, 2021.
The full results of the study can be found on the Modeling page :
An ensemble model based on early predictors to forecast COVID-19 health care demand in France, April 27, 2022, PNAS
Juliette Paireaua,b,1, Alessio Andronicoa,1, Nathanaël Hozéa, Maylis Layana, Pascal Crepeyc, Alix Roumagnacd, Marc Laviellee,f , Pierre-Yves Boëlleg, and Simon Cauchemez a
a Mathematical modelling of Infectious Diseases Unit, Institut Pasteur, Université Paris Cité, CNRS UMR 2000, 75015 Paris, France
b Direction des Maladies Infectieuses, Santé publique France, 94415 Saint Maurice, France
c Arènes-UMR 6051, RSMS-U 1309, Ecole des Hautes Etudes en Santé Publique, INSERM, CNRS, Université de Rennes, 35043 Rennes, France
d Predict Services, 34170 Castelnau-le-Lez, Francee INRIA, 91120 Palaiseau, France
f Centre de Mathématiques Appliquées, Ecole Polytechnique, CNRS, Institut Polytechnique de Paris, 91128 Palaiseau, France
g Institut Pierre Louis d'Epidémiologie et de Santé Publique, INSERM, Sorbonne Université, 75012 Paris, France
1 J.P. and A.A. contributed equally to this work