title: The effects of demographic change on disease transmission and vaccine impact in a household structured population.
abstract: The demographic structure of populations in both more developed and less developed countries is changing: increases in life expectancy and declining fertility have led to older populations and smaller households. The implications of these demographic changes for the spread and control of infectious diseases are not fully understood. Here we use an individual based model with realistic and dynamic age and household structure to demonstrate the marked effect that demographic change has on disease transmission at the population and household level. The decline in fertility is associated with a decrease in disease incidence and an increase in the age of first infection, even in the absence of vaccination or other control measures. Although large households become rarer as fertility decreases, we show that there is a proportionate increase in incidence of disease in these households as the accumulation of susceptible clusters increases the potential for explosive outbreaks. By modelling vaccination, we provide a direct comparison of the relative importance of demographic change and vaccination on incidence of disease. We highlight the increased risks associated with unvaccinated households in a low fertility setting if vaccine behaviour is correlated with household membership. We suggest that models that do not account for future demographic change, and especially its effect on household structure, may potentially overestimate the impact of vaccination.
authors.affiliation: Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, 207 Bouverie Street, The University of Melbourne, VIC 3010, Australia; Clayton School of Information Technology, Building 63, Monash University Clayton Campus, Wellington Road, Clayton, VIC 3800, Australia. Electronic address: ngeard@unimelb.edu.au.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Geard
authors.affiliation: National Centre for Epidemiology and Population Health, College of Medicine, Biology and Environment, Building 62, Cnr of Eggleston and Mills Roads, The Australian National University, Canberra, ACT 0200, Australia.
authors.forename: Kathryn
authors.initials: K
authors.lastname: Glass
authors.affiliation: Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, 207 Bouverie Street, The University of Melbourne, VIC 3010, Australia; Murdoch Childrens Research Institute, Royal Children's Hospital, Flemington Road, Parkville, VIC 3052, Australia.
authors.forename: James M
authors.initials: JM
authors.lastname: McCaw
authors.affiliation: Department of Medicine, The University of Melbourne, 4th Floor, Clinical Sciences Building, The Royal Melbourne Hospital, Royal Parade, Parkville, VIC 3050, Australia; Australian Institute of Tropical Health and Medicine, James Cook University, 1 James Cook Drive, Townsville, QLD 4811, Australia.
authors.forename: Emma S
authors.initials: ES
authors.lastname: McBryde
authors.affiliation: Clayton School of Information Technology, Building 63, Monash University Clayton Campus, Wellington Road, Clayton, VIC 3800, Australia.
authors.forename: Kevin B
authors.initials: KB
authors.lastname: Korb
authors.affiliation: Biological Sciences and Mathematics Institute, University of Warwick, Gibbet Hill Rd, Coventry CV4 7AL, United Kingdom.
authors.forename: Matt J
authors.initials: MJ
authors.lastname: Keeling
authors.affiliation: Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, 207 Bouverie Street, The University of Melbourne, VIC 3010, Australia; Murdoch Childrens Research Institute, Royal Children's Hospital, Flemington Road, Parkville, VIC 3052, Australia.
authors.forename: Jodie
authors.initials: J
authors.lastname: McVernon
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D001315:Australia / Q000453:epidemiology; D003141:Communicable Diseases / Q000453:epidemiology*; D003710:Demography / Q000706:statistics & numerical data*; D004196:Disease Outbreaks; D005191:Family Characteristics; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D017678:Sex Distribution; D014611:Vaccination / Q000706:statistics & numerical data*; D055815:Young Adult
keywords: Demographic change; Individual based model; Infectious disease; Vaccination