title: Estimating dynamic transmission model parameters for seasonal influenza by fitting to age and season-specific influenza-like illness incidence.
abstract: Dynamic transmission models are essential to design and evaluate control strategies for airborne infections. Our objective was to develop a dynamic transmission model for seasonal influenza allowing to evaluate the impact of vaccinating specific age groups on the incidence of infection, disease and mortality. Projections based on such models heavily rely on assumed 'input' parameter values. In previous seasonal influenza models, these parameter values were commonly chosen ad hoc, ignoring between-season variability and without formal model validation or sensitivity analyses. We propose to directly estimate the parameters by fitting the model to age-specific influenza-like illness (ILI) incidence data over multiple influenza seasons. We used a weighted least squares (WLS) criterion to assess model fit and applied our method to Belgian ILI data over six influenza seasons. After exploring parameter importance using symbolic regression, we evaluated a set of candidate models of differing complexity according to the number of season-specific parameters. The transmission parameters (average R0, seasonal amplitude and timing of the seasonal peak), waning rates and the scale factor used for WLS optimization, influenced the fit to the observed ILI incidence the most. Our results demonstrate the importance of between-season variability in influenza transmission and our estimates are in line with the classification of influenza seasons according to intensity and vaccine matching.
authors.affiliation: Interuniversity Institute for Biostatistics and statistical Bioinformatics, Hasselt University, Agoralaan Gebouw D, B3590 Diepenbeek, Belgium; Centre for Health Economics Research and Modelling Infectious Diseases, Vaccine & Infectious Disease Institute, University of Antwerp, Universiteitsplein 1, B2610 Wilrijk, Belgium. Electronic address: nele.goeyvaerts@uhasselt.be.
authors.forename: Nele
authors.initials: N
authors.lastname: Goeyvaerts
authors.affiliation: Interuniversity Institute for Biostatistics and statistical Bioinformatics, Hasselt University, Agoralaan Gebouw D, B3590 Diepenbeek, Belgium; Centre for Health Economics Research and Modelling Infectious Diseases, Vaccine & Infectious Disease Institute, University of Antwerp, Universiteitsplein 1, B2610 Wilrijk, Belgium; Department of Mathematics and Computer Science, University of Antwerp, Middelheimlaan 1, B2020 Antwerp, Belgium.
authors.forename: Lander
authors.initials: L
authors.lastname: Willem
authors.affiliation: Interuniversity Institute for Biostatistics and statistical Bioinformatics, Hasselt University, Agoralaan Gebouw D, B3590 Diepenbeek, Belgium; Centre for Health Economics Research and Modelling Infectious Diseases, Vaccine & Infectious Disease Institute, University of Antwerp, Universiteitsplein 1, B2610 Wilrijk, Belgium.
authors.forename: Kim
authors.initials: K
authors.lastname: Van Kerckhove
authors.affiliation: Interuniversity Institute for Biostatistics and statistical Bioinformatics, Hasselt University, Agoralaan Gebouw D, B3590 Diepenbeek, Belgium.
authors.forename: Yannick
authors.initials: Y
authors.lastname: Vandendijck
authors.affiliation: KCE - Belgian Health Care Knowledge Centre, Boulevard du Jardin Botanique 55, B1000 Brussels, Belgium.
authors.forename: Germaine
authors.initials: G
authors.lastname: Hanquet
authors.affiliation: Centre for Health Economics Research and Modelling Infectious Diseases, Vaccine & Infectious Disease Institute, University of Antwerp, Universiteitsplein 1, B2610 Wilrijk, Belgium.
authors.forename: Philippe
authors.initials: P
authors.lastname: Beutels
authors.affiliation: Interuniversity Institute for Biostatistics and statistical Bioinformatics, Hasselt University, Agoralaan Gebouw D, B3590 Diepenbeek, Belgium; Centre for Health Economics Research and Modelling Infectious Diseases, Vaccine & Infectious Disease Institute, University of Antwerp, Universiteitsplein 1, B2610 Wilrijk, Belgium.
authors.forename: Niel
authors.initials: N
authors.lastname: Hens
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007251:Influenza, Human / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D012621:Seasons; D055815:Young Adult
keywords: Influenza; Mathematical model; Parameter estimation; Reproduction number; Seasonal variability