TY - JOUR
T1 - Prolonging herd immunity to cholera via vaccination
T2 - Accounting for human mobility and waning vaccine effects
AU - Peak, Corey M.
AU - Reilly, Amanda L.
AU - Azman, Andrew S.
AU - Buckee, Caroline O.
N1 - Funding Information:
CMP and COB were supported by Cooperative Agreement U54GM088558 from the National Institute of General Medical Sciences (https://www.nigms.nih.gov/). CMP was also supported by National Research Service Award T32AI007535-16A1 (https://grants.nih.gov/). ASA was supported by the Bill and Melinda Gates Foundation (OPP1089243)(http://www.gatesfoundation.org) and the DOVE project (OPP153556) (https://www.stopcholera.org/). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of General Medical Sciences or the National Institutes of Health. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. We thank members of the Global Task Force on Cholera Control Working Groups for helpful discussions.
Publisher Copyright:
© 2018 Peak et al.
PY - 2018/2/28
Y1 - 2018/2/28
N2 - Background: Oral cholera vaccination is an approach to preventing outbreaks in at-risk settings and controlling cholera in endemic settings. However, vaccine-derived herd immunity may be short-lived due to interactions between human mobility and imperfect or waning vaccine efficacy. As the supply and utilization of oral cholera vaccines grows, critical questions related to herd immunity are emerging, including: who should be targeted; when should revaccination be performed; and why have cholera outbreaks occurred in recently vaccinated populations? Methods and findings: We use mathematical models to simulate routine and mass oral cholera vaccination in populations with varying degrees of migration, transmission intensity, and vaccine coverage. We show that migration and waning vaccine efficacy strongly influence the duration of herd immunity while birth and death rates have relatively minimal impacts. As compared to either periodic mass vaccination or routine vaccination alone, a community could be protected longer by a blended “Mass and Maintain” strategy. We show that vaccination may be best targeted at populations with intermediate degrees of mobility as compared to communities with very high or very low population turnover. Using a case study of an internally displaced person camp in South Sudan which underwent high-coverage mass vaccination in 2014 and 2015, we show that waning vaccine direct effects and high population turnover rendered the camp over 80% susceptible at the time of the cholera outbreak beginning in October 2016. Conclusions: Oral cholera vaccines can be powerful tools for quickly protecting a population for a period of time that depends critically on vaccine coverage, vaccine efficacy over time, and the rate of population turnover through human mobility. Due to waning herd immunity, epidemics in vaccinated communities are possible but become less likely through complementary interventions or data-driven revaccination strategies.
AB - Background: Oral cholera vaccination is an approach to preventing outbreaks in at-risk settings and controlling cholera in endemic settings. However, vaccine-derived herd immunity may be short-lived due to interactions between human mobility and imperfect or waning vaccine efficacy. As the supply and utilization of oral cholera vaccines grows, critical questions related to herd immunity are emerging, including: who should be targeted; when should revaccination be performed; and why have cholera outbreaks occurred in recently vaccinated populations? Methods and findings: We use mathematical models to simulate routine and mass oral cholera vaccination in populations with varying degrees of migration, transmission intensity, and vaccine coverage. We show that migration and waning vaccine efficacy strongly influence the duration of herd immunity while birth and death rates have relatively minimal impacts. As compared to either periodic mass vaccination or routine vaccination alone, a community could be protected longer by a blended “Mass and Maintain” strategy. We show that vaccination may be best targeted at populations with intermediate degrees of mobility as compared to communities with very high or very low population turnover. Using a case study of an internally displaced person camp in South Sudan which underwent high-coverage mass vaccination in 2014 and 2015, we show that waning vaccine direct effects and high population turnover rendered the camp over 80% susceptible at the time of the cholera outbreak beginning in October 2016. Conclusions: Oral cholera vaccines can be powerful tools for quickly protecting a population for a period of time that depends critically on vaccine coverage, vaccine efficacy over time, and the rate of population turnover through human mobility. Due to waning herd immunity, epidemics in vaccinated communities are possible but become less likely through complementary interventions or data-driven revaccination strategies.
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U2 - 10.1371/journal.pntd.0006257
DO - 10.1371/journal.pntd.0006257
M3 - Article
C2 - 29489815
AN - SCOPUS:85044333250
SN - 1935-2727
VL - 12
JO - PLoS neglected tropical diseases
JF - PLoS neglected tropical diseases
IS - 2
M1 - e0006257
ER -