title: Reproduction numbers for epidemic models with households and other social structures II: Comparisons and implications for vaccination.
abstract: In this paper we consider epidemic models of directly transmissible SIR (susceptible → infective → recovered) and SEIR (with an additional latent class) infections in fully-susceptible populations with a social structure, consisting either of households or of households and workplaces. We review most reproduction numbers defined in the literature for these models, including the basic reproduction number R0 introduced in the companion paper of this, for which we provide a simpler, more elegant derivation. Extending previous work, we provide a complete overview of the inequalities among these reproduction numbers and resolve some open questions. Special focus is put on the exponential-growth-associated reproduction number Rr, which is loosely defined as the estimate of R0 based on the observed exponential growth of an emerging epidemic obtained when the social structure is ignored. We show that for the vast majority of the models considered in the literature Rr ≥ R0 when R0 ≥ 1 and Rr ≤ R0 when R0 ≤ 1. We show that, in contrast to models without social structure, vaccination of a fraction 1-1/R0 of the population, chosen uniformly at random, with a perfect vaccine is usually insufficient to prevent large epidemics. In addition, we provide significantly sharper bounds than the existing ones for bracketing the critical vaccination coverage between two analytically tractable quantities, which we illustrate by means of extensive numerical examples.
authors: School of Mathematical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK.
authors: Frank
authors: F
authors: Ball
authors: Warwick Infectious Disease Epidemiology Research Centre (WIDER) and Warwick Mathematics Institute, University of Warwick, Coventry CV4 7AL, UK. Electronic address: l.pellis@warwick.ac.uk.
authors: Lorenzo
authors: L
authors: Pellis
authors: Department of Mathematics, Stockholm University, Stockholm 106 91, Sweden.
authors: Pieter
authors: P
authors: Trapman
mesh_terms: D050936:Basic Reproduction Number / Q000706:statistics & numerical data*; D003141:Communicable Diseases / Q000453:epidemiology; D058872:Epidemics / Q000517:prevention & control / Q000706:statistics & numerical data*; D005191:Family Characteristics; D006801:Humans; D055641:Mathematical Concepts; D008954:Models, Biological; D012931:Social Environment; D014611:Vaccination; D017132:Workplace
keywords: Basic reproduction number; Exponential growth rate; Household; SIR epidemic; Social structure; Vaccination