Characterizing the impact of spatial clustering of susceptibility for measles elimination
Authored by Shaun A Truelove, Matthew Graham, William J Moss, C Jessica E Metcalf, Matthew J Ferrari, Justin Lessler
Date Published: 2019
DOI: 10.1016/j.vaccine.2018.12.012
Sponsors:
Bill and Melinda Gates Foundation
Platforms:
R
Model Documentation:
Other Narrative
Mathematical description
Model Code URLs:
Model code not found
Abstract
Measles elimination efforts are primarily focused on achieving and
maintaining national vaccination coverage goals, based on estimates of
the critical vaccination threshold (V-c): the proportion of the
population that must be immune to prevent sustained epidemics.
Traditionally, V-c estimates assume evenly mixing populations, an
invalid assumption. If susceptible individuals preferentially contact
one another, communities may remain vulnerable to epidemics even when
vaccination coverage targets are met at the national level. Here we
present a simple method to estimate V-c and the effective reproductive
number, R, while accounting for spatial clustering of susceptibility.
For measles, assuming R-0 = 15 and 95\% population immunity, adjustment
for high clustering of susceptibility increases R from 0.75 to 1.29, V-c
from 93\% to 96\%, and outbreak probability after a single introduction
from <1\% to 23\%. The impact of clustering remains minimal until
vaccination coverage nears elimination levels. We illustrate our
approach using Demographic and Health Survey data from Tanzania and show
how non-vaccination clustering potentially contributed to continued
endemic transmission of measles virus during the last two decades. Our
approach demonstrates why high national vaccination coverage sometimes
fails to achieve measles elimination, and that a shift from national to
subnational focus is needed as countries approach elimination. (C) 2018
The Authors. Published by Elsevier Ltd.
Tags
Heterogeneity
Clustering
Community
Progress
transmission
Vaccination
Children
Foot
Rubella
Measles
Disease
transmission
Effective reproductive number
Critical vaccination threshold
Critical immunity threshold
Outbreak risk
Stochastic individual-based
model
Vaccination coverage
Mouth epidemic
Herd-immunity
Exemptions