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Comparative effectiveness of different strategies of oral cholera vaccination in bangladesh: a modeling study.

Dimitrov DT, Troeger C, Halloran ME, Longini IM, Chao DL - PLoS Negl Trop Dis (2014)

Bottom Line: Killed, oral cholera vaccines have proven safe and effective, and several large-scale mass cholera vaccination efforts have demonstrated the feasibility of widespread deployment.We conclude that continuous mass vaccination would be more effective against endemic cholera than periodic campaigns.Careful consideration must be made before generalizing these results to other regions.

View Article: PubMed Central - PubMed

Affiliation: Center for Statistics and Quantitative Infectious Diseases; Vaccine and Infectious Disease Division; Fred Hutchinson Cancer Research Center; Seattle, Washington, United States of America.

ABSTRACT

Background: Killed, oral cholera vaccines have proven safe and effective, and several large-scale mass cholera vaccination efforts have demonstrated the feasibility of widespread deployment. This study uses a mathematical model of cholera transmission in Bangladesh to examine the effectiveness of potential vaccination strategies.

Methods & findings: We developed an age-structured mathematical model of cholera transmission and calibrated it to reproduce the dynamics of cholera in Matlab, Bangladesh. We used the model to predict the effectiveness of different cholera vaccination strategies over a period of 20 years. We explored vaccination programs that targeted one of three increasingly focused age groups (the entire vaccine-eligible population of age one year and older, children of ages 1 to 14 years, or preschoolers of ages 1 to 4 years) and that could occur either as campaigns recurring every five years or as continuous ongoing vaccination efforts. Our modeling results suggest that vaccinating 70% of the population would avert 90% of cholera cases in the first year but that campaign and continuous vaccination strategies differ in effectiveness over 20 years. Maintaining 70% coverage of the population would be sufficient to prevent sustained transmission of endemic cholera in Matlab, while vaccinating periodically every five years is less effective. Selectively vaccinating children 1-14 years old would prevent the most cholera cases per vaccine administered in both campaign and continuous strategies.

Conclusions: We conclude that continuous mass vaccination would be more effective against endemic cholera than periodic campaigns. Vaccinating children averts more cases per dose than vaccinating all age groups, although vaccinating only children is unlikely to control endemic cholera in Bangladesh. Careful consideration must be made before generalizing these results to other regions.

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Flow diagram of the mathematical model of cholera transmission.Individuals are aggregated in compartments by cholera status as susceptible unvaccinated (S), susceptible vaccinated (V), cholera cases (I), asymptomatically infected (A), and recovered (R). The concentration of Vibrio cholerae in the environment is tracked in a separate compartment (W). Proportion p of the susceptibles and proportion q of the vaccinated who become infected are symptomatic (cholera cases), and a fraction r of these are reported and used to fit the model to surveillance data. Infected individuals shed bacteria into the environment and cause indirect transmission of Cholera (dashed lines). The simulated population is additionally stratified by age (not shown). A complete description of the model including the expressions for the forces of infections (λ and λV) is presented in Text S1.
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pntd-0003343-g001: Flow diagram of the mathematical model of cholera transmission.Individuals are aggregated in compartments by cholera status as susceptible unvaccinated (S), susceptible vaccinated (V), cholera cases (I), asymptomatically infected (A), and recovered (R). The concentration of Vibrio cholerae in the environment is tracked in a separate compartment (W). Proportion p of the susceptibles and proportion q of the vaccinated who become infected are symptomatic (cholera cases), and a fraction r of these are reported and used to fit the model to surveillance data. Infected individuals shed bacteria into the environment and cause indirect transmission of Cholera (dashed lines). The simulated population is additionally stratified by age (not shown). A complete description of the model including the expressions for the forces of infections (λ and λV) is presented in Text S1.

Mentions: We developed an age-structured mathematical model of cholera transmission. Compartments in the model are unvaccinated susceptible (S), vaccinated susceptible (V), symptomatically infected (I), asymptomatically infected (A), or recovered and immune (R) from cholera (Figure 1). The concentration of V. cholerae in the environment (water) is tracked in an additional compartment (W). Susceptible individuals may become infected by direct contact with infected individuals (direct transmission) or by exposure to V. cholerae in the environment (indirect transmission). A complete description of the model is given in Text S1.


Comparative effectiveness of different strategies of oral cholera vaccination in bangladesh: a modeling study.

Dimitrov DT, Troeger C, Halloran ME, Longini IM, Chao DL - PLoS Negl Trop Dis (2014)

Flow diagram of the mathematical model of cholera transmission.Individuals are aggregated in compartments by cholera status as susceptible unvaccinated (S), susceptible vaccinated (V), cholera cases (I), asymptomatically infected (A), and recovered (R). The concentration of Vibrio cholerae in the environment is tracked in a separate compartment (W). Proportion p of the susceptibles and proportion q of the vaccinated who become infected are symptomatic (cholera cases), and a fraction r of these are reported and used to fit the model to surveillance data. Infected individuals shed bacteria into the environment and cause indirect transmission of Cholera (dashed lines). The simulated population is additionally stratified by age (not shown). A complete description of the model including the expressions for the forces of infections (λ and λV) is presented in Text S1.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4256212&req=5

pntd-0003343-g001: Flow diagram of the mathematical model of cholera transmission.Individuals are aggregated in compartments by cholera status as susceptible unvaccinated (S), susceptible vaccinated (V), cholera cases (I), asymptomatically infected (A), and recovered (R). The concentration of Vibrio cholerae in the environment is tracked in a separate compartment (W). Proportion p of the susceptibles and proportion q of the vaccinated who become infected are symptomatic (cholera cases), and a fraction r of these are reported and used to fit the model to surveillance data. Infected individuals shed bacteria into the environment and cause indirect transmission of Cholera (dashed lines). The simulated population is additionally stratified by age (not shown). A complete description of the model including the expressions for the forces of infections (λ and λV) is presented in Text S1.
Mentions: We developed an age-structured mathematical model of cholera transmission. Compartments in the model are unvaccinated susceptible (S), vaccinated susceptible (V), symptomatically infected (I), asymptomatically infected (A), or recovered and immune (R) from cholera (Figure 1). The concentration of V. cholerae in the environment (water) is tracked in an additional compartment (W). Susceptible individuals may become infected by direct contact with infected individuals (direct transmission) or by exposure to V. cholerae in the environment (indirect transmission). A complete description of the model is given in Text S1.

Bottom Line: Killed, oral cholera vaccines have proven safe and effective, and several large-scale mass cholera vaccination efforts have demonstrated the feasibility of widespread deployment.We conclude that continuous mass vaccination would be more effective against endemic cholera than periodic campaigns.Careful consideration must be made before generalizing these results to other regions.

View Article: PubMed Central - PubMed

Affiliation: Center for Statistics and Quantitative Infectious Diseases; Vaccine and Infectious Disease Division; Fred Hutchinson Cancer Research Center; Seattle, Washington, United States of America.

ABSTRACT

Background: Killed, oral cholera vaccines have proven safe and effective, and several large-scale mass cholera vaccination efforts have demonstrated the feasibility of widespread deployment. This study uses a mathematical model of cholera transmission in Bangladesh to examine the effectiveness of potential vaccination strategies.

Methods & findings: We developed an age-structured mathematical model of cholera transmission and calibrated it to reproduce the dynamics of cholera in Matlab, Bangladesh. We used the model to predict the effectiveness of different cholera vaccination strategies over a period of 20 years. We explored vaccination programs that targeted one of three increasingly focused age groups (the entire vaccine-eligible population of age one year and older, children of ages 1 to 14 years, or preschoolers of ages 1 to 4 years) and that could occur either as campaigns recurring every five years or as continuous ongoing vaccination efforts. Our modeling results suggest that vaccinating 70% of the population would avert 90% of cholera cases in the first year but that campaign and continuous vaccination strategies differ in effectiveness over 20 years. Maintaining 70% coverage of the population would be sufficient to prevent sustained transmission of endemic cholera in Matlab, while vaccinating periodically every five years is less effective. Selectively vaccinating children 1-14 years old would prevent the most cholera cases per vaccine administered in both campaign and continuous strategies.

Conclusions: We conclude that continuous mass vaccination would be more effective against endemic cholera than periodic campaigns. Vaccinating children averts more cases per dose than vaccinating all age groups, although vaccinating only children is unlikely to control endemic cholera in Bangladesh. Careful consideration must be made before generalizing these results to other regions.

Show MeSH
Related in: MedlinePlus