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The contribution of neighbours to an individual's risk of typhoid outcome

  • D. L. CHAO (a1), J. K. PARK (a2), F. MARKS (a2), R. L. OCHIAI (a2), I. M. LONGINI (a3) and M. E. HALLORAN (a1) (a4)...

Summary

An individual's risk of infection from an infectious agent can depend on both the individual's own risk and protective factors and those of individuals in the same community. We hypothesize that an individual's exposure to an infectious agent is associated with the risks of infection of those living nearby, whether their risks are modified by pharmaceutical interventions or by other factors, because of the potential for transmission from them. For example, unvaccinated individuals living in a highly vaccinated community can benefit from indirect protection, or living near more children in a typhoid-endemic region (where children are at highest risk) might result in more exposure to typhoid. We tested this hypothesis using data from a cluster-randomized typhoid vaccine trial. We first estimated each individual's relative risk of confirmed typhoid outcome using their vaccination status and age. We defined a new covariate, potential exposure, to be the sum of the relative risks of all who live within 100 m of each person. We found that potential exposure was significantly associated with an individual's typhoid outcome, and adjusting for potential exposure affected estimates of vaccine efficacy. We suggest that it is useful and feasible to adjust for spatially heterogeneous distributions of individual-level risk factors, but further work is required to develop and test such approaches.

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Copyright

This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/3.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.

Corresponding author

* Author for correspondence: D. L. Chao, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave N, M2-B167, Seattle, WA 98109, USA. (Email: dchao@fhcrc.org)

References

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1. Fox, JP. Herd immunity and measles. Reviews of Infectious Diseases 1983; 5: 463466.
2. Fine, PE. Herd immunity: history, theory, practice. Epidemiologic Reviews 1993; 15: 265302.
3. Fine, P, Eames, K, Heymann, DL. ‘Herd immunity’: a rough guide. Clinical Infectious Diseases 2011; 52: 911916.
4. Mogasale, V, et al. Burden of typhoid fever in low-income and middle-income countries: a systematic, literature-based update with risk-factor adjustment. Lancet Global Health 2014; 2: e57080.
5. Sinha, A, et al. Typhoid fever in children aged less than 5 years. Lancet 1999; 354: 734737.
6. Crump, JA, Luby, SP, Mintz, ED. The global burden of typhoid fever. Bulletin of the World Health Organization 2004; 82: 346353.
7. Sur, D, et al. Comparisons of predictors for typhoid and paratyphoid fever in Kolkata, India. BMC Public Health 2007; 7: 289.
8. Ochiai, RL, et al. A study of typhoid fever in five Asian countries: disease burden and implications for controls. Bulletin of the World Health Organization 2008; 86: 260268.
9. Khan, MI, et al. Risk factors associated with typhoid fever in children aged 2–16 years in Karachi, Pakistan. Epidemiology and Infection 2012; 140: 665672.
10. Anwar, E, et al. Vaccines for preventing typhoid fever. Cochrane Database of Systematic Reviews 2014. Issue 1: Art. no. CD001261.
11. Sur, D, et al. A cluster-randomized effectiveness trial of Vi typhoid vaccine in India. New England Journal of Medicine 2009; 361: 335344.
12. Ali, M, et al. Impact of Vi vaccination on spatial patterns of typhoid fever in the slums of Kolkata, India. Vaccine 2011; 29: 90519056.
13. R Core Team. R: A language and environment for statistical computing. Vienna, Austria: R Foundation for Statistical Computing, 2013 (http://www.R-project.org).
14. Therneau, TM, Grambsch, PM. Modeling Survival Data: Extending the Cox Model. New York: Springer, 2000.
15. Therneau, TM. A package for survival analysis in S. R package version 2.37-4 (http://CRAN.R-project.org/package=survival), 2013.
16. Efron, B. Efficiency of Cox's likelihood function for censored data. Journal of the American Statistical Association 1997; 72: 557565.
17. Venables, WN, Ripley, BD. Modern Applied Statistics with S, 4th edn. New York: Springer, 2002.
18. Halloran, ME, Longini, IM Jr., Struchiner, CJ. Design and Analysis of Vaccine Studies. New York: Springer, 2010.
19. Emch, M, et al. Spatial and environmental connectivity analysis in a cholera vaccine trial. Social Science & Medicine 2009; 68: 631637.
20. Emch, M, et al. Efficacy calculation in randomized trials: global or local measures? Health & Place 2007; 13: 238248.

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