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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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Modeling 5-year campaign and continuous vaccination strategies for vaccine with different coverage levels and targeting different age groups.A) Overall effectiveness and B) vaccinations per case prevented by mass vaccination campaigns that occur every 5 years. C) Overall effectiveness and D) vaccinations per case prevented by continuous vaccination. We assume that the vaccine protects for an average of 5 years and is less effective among children from ages 1 to 4 years (40% efficacy) than among older individuals (65% efficacy). Overall effectiveness is the prevented fraction of cholera cases over 20 years. The boxes represent the interquartile range and the whiskers cover 90% of the results from 100 simulations per scenario with parameters of seasonal environmental exposure sampled from ranges in Table S3. Dashed lines show the effectiveness if only direct effects of the vaccine are considered.
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pntd-0003343-g004: Modeling 5-year campaign and continuous vaccination strategies for vaccine with different coverage levels and targeting different age groups.A) Overall effectiveness and B) vaccinations per case prevented by mass vaccination campaigns that occur every 5 years. C) Overall effectiveness and D) vaccinations per case prevented by continuous vaccination. We assume that the vaccine protects for an average of 5 years and is less effective among children from ages 1 to 4 years (40% efficacy) than among older individuals (65% efficacy). Overall effectiveness is the prevented fraction of cholera cases over 20 years. The boxes represent the interquartile range and the whiskers cover 90% of the results from 100 simulations per scenario with parameters of seasonal environmental exposure sampled from ranges in Table S3. Dashed lines show the effectiveness if only direct effects of the vaccine are considered.

Mentions: We compared the effectiveness of targeting different age groups with campaigns every five years. Our modeling results suggest that vaccinating everyone (100% of) one year old and older at 5-year intervals would prevent 89% of cholera cases over 20 years (Figure 4A, red boxes). The efficiency of the 5-year campaigns decreases with higher coverage, with the number of vaccinations per case averted (VPC) rising from 11 to 14 (Figure 4B). Mass vaccination of all children 1 to 14 years old at 5-year intervals would prevent approximately 33% of cholera cases (Figure 4A, blue boxes) while vaccinating all preschoolers would prevent only 6% of cholera cases over 20 years (Figure 4A, green boxes). Because the proportion of the population protected by vaccine drops between campaigns, this vaccination strategy is not able to suppress cholera activity over 20 years, even at 100% coverage (Figure 4A). Targeting children (1 to 14 years old) is most efficient; requiring about 11 VPC over a wide range of vaccination coverage levels (Figure 4B). Targeting those 1 to 4 years old is less efficient, primarily because of the lower vaccine efficacy in this group.


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)

Modeling 5-year campaign and continuous vaccination strategies for vaccine with different coverage levels and targeting different age groups.A) Overall effectiveness and B) vaccinations per case prevented by mass vaccination campaigns that occur every 5 years. C) Overall effectiveness and D) vaccinations per case prevented by continuous vaccination. We assume that the vaccine protects for an average of 5 years and is less effective among children from ages 1 to 4 years (40% efficacy) than among older individuals (65% efficacy). Overall effectiveness is the prevented fraction of cholera cases over 20 years. The boxes represent the interquartile range and the whiskers cover 90% of the results from 100 simulations per scenario with parameters of seasonal environmental exposure sampled from ranges in Table S3. Dashed lines show the effectiveness if only direct effects of the vaccine are considered.
© Copyright Policy
Related In: Results  -  Collection

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

pntd-0003343-g004: Modeling 5-year campaign and continuous vaccination strategies for vaccine with different coverage levels and targeting different age groups.A) Overall effectiveness and B) vaccinations per case prevented by mass vaccination campaigns that occur every 5 years. C) Overall effectiveness and D) vaccinations per case prevented by continuous vaccination. We assume that the vaccine protects for an average of 5 years and is less effective among children from ages 1 to 4 years (40% efficacy) than among older individuals (65% efficacy). Overall effectiveness is the prevented fraction of cholera cases over 20 years. The boxes represent the interquartile range and the whiskers cover 90% of the results from 100 simulations per scenario with parameters of seasonal environmental exposure sampled from ranges in Table S3. Dashed lines show the effectiveness if only direct effects of the vaccine are considered.
Mentions: We compared the effectiveness of targeting different age groups with campaigns every five years. Our modeling results suggest that vaccinating everyone (100% of) one year old and older at 5-year intervals would prevent 89% of cholera cases over 20 years (Figure 4A, red boxes). The efficiency of the 5-year campaigns decreases with higher coverage, with the number of vaccinations per case averted (VPC) rising from 11 to 14 (Figure 4B). Mass vaccination of all children 1 to 14 years old at 5-year intervals would prevent approximately 33% of cholera cases (Figure 4A, blue boxes) while vaccinating all preschoolers would prevent only 6% of cholera cases over 20 years (Figure 4A, green boxes). Because the proportion of the population protected by vaccine drops between campaigns, this vaccination strategy is not able to suppress cholera activity over 20 years, even at 100% coverage (Figure 4A). Targeting children (1 to 14 years old) is most efficient; requiring about 11 VPC over a wide range of vaccination coverage levels (Figure 4B). Targeting those 1 to 4 years old is less efficient, primarily because of the lower vaccine efficacy in this group.

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