title: The impact of demographic changes on the epidemiology of herpes zoster: Spain as a case study.
abstract: Varicella zoster virus (VZV) causes varicella upon first exposure and may reactivate later in life into herpes zoster (HZ), with a risk that is thought to be reduced by re-exposures to VZV. Given the decades-long time scales of reactivation and its dependence on the accumulation of re-exposure episodes, adopting a long-term perspective may be useful to correctly interpret current epidemiological trends of VZV. In this study, we investigate the possible impact of demographic changes on varicella and HZ in Spain, using an age-structured mathematical model informed with historical demographic data and calibrated against age-specific profiles of varicella seroprevalence and HZ incidence data. The model qualitatively reproduces the remarkable growth of HZ incidence observed in Spain between 1997 and 2004, before the introduction of varicella vaccination programmes. We demonstrate that this growth may be partially ascribed to the reduction of varicella circulation that followed the overall decline of the birth rate in the twentieth century. Model predictions further suggest that, even under the most optimistic projections, HZ incidence will continue its rise until at least 2040. Considering the effect of demographic changes can help interpreting variations in epidemiological trends of HZ, contributing to a more accurate evaluation of vaccination programmes against VZV.
authors.affiliation: Center for Information Technology, Bruno Kessler Foundation, Trento, Italy Department of Mathematics, University of Trento, Trento, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Marziano
authors.affiliation: Center for Information Technology, Bruno Kessler Foundation, Trento, Italy DONDENA Centre for Research on Social Dynamics, Bocconi University, Milan, Italy.
authors.forename: Piero
authors.initials: P
authors.lastname: Poletti
authors.affiliation: Center for Information Technology, Bruno Kessler Foundation, Trento, Italy Trento Rise, Trento, Italy.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Guzzetta
authors.affiliation: Center for Information Technology, Bruno Kessler Foundation, Trento, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Ajelli
authors.affiliation: Department of Economics and Management, Pisa University, Pisa, Italy.
authors.forename: Piero
authors.initials: P
authors.lastname: Manfredi
authors.affiliation: Center for Information Technology, Bruno Kessler Foundation, Trento, Italy merler@fbk.eu.
authors.forename: Stefano
authors.initials: S
authors.lastname: Merler
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002644:Chickenpox / Q000453:epidemiology* / Q000517:prevention & control / Q000821:virology; D002648:Child; D002675:Child, Preschool; D006562:Herpes Zoster / Q000453:epidemiology* / Q000517:prevention & control / Q000821:virology; D014645:Herpesvirus 3, Human / Q000302:isolation & purification / Q000502:physiology*; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008875:Middle Aged; D008962:Models, Theoretical; D011157:Population Dynamics; D015995:Prevalence; D016036:Seroepidemiologic Studies; D013030:Spain / Q000453:epidemiology; D014611:Vaccination; D055815:Young Adult
keywords: demographic transition; herpes zoster; mathematical modelling; varicella