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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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Comparison of one-time mass vaccination, vaccination campaigns that occur every 5 years, and continuous vaccination.The one-time vaccination targets 70% of the vaccine-eligible population (those one year old and older) for vaccination, the 5-year campaigns target 70% of the population every 5 years, and the continuous vaccination strategy targets 70% of the population at the beginning of the first year then vaccinates at a constant rate starting in year 2. Vaccine is less effective for children aged 1–4 (40% efficacy) than for older children and adults (65% efficacy). Temporal dynamics of A) the fraction of the population protected by vaccine; B) annual cholera cases; C) the overall effectiveness in terms of prevented fraction of cholera cases when different vaccination strategies are implemented; and D) total number of vaccinations for different strategies over 10 and 20 years.
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pntd-0003343-g003: Comparison of one-time mass vaccination, vaccination campaigns that occur every 5 years, and continuous vaccination.The one-time vaccination targets 70% of the vaccine-eligible population (those one year old and older) for vaccination, the 5-year campaigns target 70% of the population every 5 years, and the continuous vaccination strategy targets 70% of the population at the beginning of the first year then vaccinates at a constant rate starting in year 2. Vaccine is less effective for children aged 1–4 (40% efficacy) than for older children and adults (65% efficacy). Temporal dynamics of A) the fraction of the population protected by vaccine; B) annual cholera cases; C) the overall effectiveness in terms of prevented fraction of cholera cases when different vaccination strategies are implemented; and D) total number of vaccinations for different strategies over 10 and 20 years.

Mentions: We compare the effectiveness over 20 years of one-time mass vaccination, recurring campaigns every five years, and continuous vaccination targeting 70% of all individuals one year old and older (Figure 3). All three vaccination strategies avert about 94% of the cholera cases in the first year (Figures 3B and 3C). Vaccination of 50% of the population would reduce the incidence of cholera by 88% in the first year following vaccination (Figure S3 in Text S2). This is consistent with projections from a previous modeling study that found vaccination coverage of 50% would be sufficient to avert 93% of cholera cases in one season in Matlab [16]. With a one-time mass vaccination campaign, cholera incidence rebounds as protection from vaccine wanes and new susceptible individuals are born, and the overall effectiveness of the campaign is only about 20% after 20 years (Figure 3C).


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)

Comparison of one-time mass vaccination, vaccination campaigns that occur every 5 years, and continuous vaccination.The one-time vaccination targets 70% of the vaccine-eligible population (those one year old and older) for vaccination, the 5-year campaigns target 70% of the population every 5 years, and the continuous vaccination strategy targets 70% of the population at the beginning of the first year then vaccinates at a constant rate starting in year 2. Vaccine is less effective for children aged 1–4 (40% efficacy) than for older children and adults (65% efficacy). Temporal dynamics of A) the fraction of the population protected by vaccine; B) annual cholera cases; C) the overall effectiveness in terms of prevented fraction of cholera cases when different vaccination strategies are implemented; and D) total number of vaccinations for different strategies over 10 and 20 years.
© Copyright Policy
Related In: Results  -  Collection

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

pntd-0003343-g003: Comparison of one-time mass vaccination, vaccination campaigns that occur every 5 years, and continuous vaccination.The one-time vaccination targets 70% of the vaccine-eligible population (those one year old and older) for vaccination, the 5-year campaigns target 70% of the population every 5 years, and the continuous vaccination strategy targets 70% of the population at the beginning of the first year then vaccinates at a constant rate starting in year 2. Vaccine is less effective for children aged 1–4 (40% efficacy) than for older children and adults (65% efficacy). Temporal dynamics of A) the fraction of the population protected by vaccine; B) annual cholera cases; C) the overall effectiveness in terms of prevented fraction of cholera cases when different vaccination strategies are implemented; and D) total number of vaccinations for different strategies over 10 and 20 years.
Mentions: We compare the effectiveness over 20 years of one-time mass vaccination, recurring campaigns every five years, and continuous vaccination targeting 70% of all individuals one year old and older (Figure 3). All three vaccination strategies avert about 94% of the cholera cases in the first year (Figures 3B and 3C). Vaccination of 50% of the population would reduce the incidence of cholera by 88% in the first year following vaccination (Figure S3 in Text S2). This is consistent with projections from a previous modeling study that found vaccination coverage of 50% would be sufficient to avert 93% of cholera cases in one season in Matlab [16]. With a one-time mass vaccination campaign, cholera incidence rebounds as protection from vaccine wanes and new susceptible individuals are born, and the overall effectiveness of the campaign is only about 20% after 20 years (Figure 3C).

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