Long-term changes in endemic threshold populations for pertussis in England and Wales: A spatiotemporal analysis of Lancashire and South Wales, 1940-69.

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From: Social Science & Medicine(Vol. 288)
Publisher: Elsevier Science Publishers
Document Type: Report; Brief article
Length: 406 words

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Abstract :

Keywords England and Wales; Endemic threshold; Disease persistence; Childhood infections; Geographical connectivity; Pertussis Highlights * Endemic threshold estimates vary considerably by region over space and time. * Divergent spatial structures and connectivity influence endemic persistence. * Increased population density limits growth of endemic threshold after vaccination. * Endemic threshold population can serve as guide for spatially targeted vaccination. * Pertussis vaccination increases fadeout duration and reduces rate of reintroduction. Abstract Metapopulation dynamics play a critical role in driving endemic persistence and transmission of childhood infections. The endemic threshold concept, also referred to as critical community size (CCS), is a key example and is defined as the minimum population size required to sustain a continuous chain of infection transmission. The concept is fundamental to the implementation of effective vaccine-based disease control programmes. Vaccination serves to increase endemic threshold population size, promoting disease fadeout and eventual elimination of infection. To date, empirical investigations of the relationship between vaccination and endemic threshold population size have tended to focus on isolated populations in island communities. Very few studies have examined endemic threshold dynamics in 'mainland' regional populations with complex hierarchical spatial structures and varying levels of connectivity between subpopulations. The present paper provides the first spatially explicit analysis of the temporal changes in endemic threshold populations for one vaccine-preventable childhood infection (pertussis) in two dynamic regions of England and Wales: Lancashire and South Wales. Drawing upon weekly disease records of the Registrar-General of England and Wales over a 30-year period (January 1940--December 1969) regression techniques were used to estimate the endemic threshold size for pertussis in the two study regions. Survival analyses were performed to compare disease fadeout duration and probability for both regions in the pre-vaccine and vaccine eras, respectively. Our findings reveal the introduction of mass vaccination led to a considerable increase in threshold size for both Lancashire (~387,333) and South Wales (~1,460,667). Significant growth in fadeout duration was observed in the vaccine era for pertussis non-hotspots in both regions, consistent with geographical synchronisation of epidemic activity. Regional differences in endemic threshold populations reflect significant regional variations in spatial connectivity, population dispersion and level of geographical isolation. Author Affiliation: School of Geography, University of Nottingham, University Park, Nottingham, NG7 2RD, UK * Corresponding author. School of Geography, University of Nottingham, University Park, Nottingham, NG7 2RD, United Kingdom. Article History: Revised 23 July 2020; Accepted 12 August 2020 Byline: Alastair D. Munro [alastair.munro@nottingham.ac.uk] (*), Matthew Smallman-Raynor, Adam C. Algar

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Gale Document Number: GALE|A679455830