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Re-evaluating herd protection by Vi typhoid vaccine in a cluster randomized trial
- Source :
- International Health
- Publication Year :
- 2020
- Publisher :
- Oxford University Press (OUP), 2020.
-
Abstract
- Background In a cluster randomized trial (CRT) of a Vi polysaccharide vaccine against typhoid in the slums of Kolkata we found evidence of vaccine herd protection. However, transmission of typhoid into clusters from the outside likely occurred in this densely populated setting, which could have diminished our estimates of vaccine herd protection. Methods Eighty clusters (40 in each arm) were randomised to receive a single dose of either Vi or inactivated hepatitis A vaccine. We analysed protection for the entire cluster and for subclusters consisting of residents of the innermost households. Results During 2 y of follow-up, total protection was 61% (95% CI 41 to 75), overall protection was 57% (95% CI 37 to 71) and indirect protection was 44% (95% CI 2 to 69). Analyses of the innermost 75% and 50% of households of the clusters showed similar findings. However, in the innermost 25% of households of the clusters, total protection was 82% (95% CI 48 to 94) and overall protection was 66% (95% CI 27 to 84). There was not a sufficient sample size to demonstrate such a trend for indirect protection in these innermost households. Conclusions The findings suggest that analyses of the entire cluster may have led to underestimation of herd protection against typhoid by Vi vaccine and that restriction of the analyses to the inner subclusters may have led to a more accurate estimation of vaccine herd effects.
- Subjects :
- Adult
Immunity, Herd
Male
Health (social science)
Adolescent
Accurate estimation
030231 tropical medicine
Hepatitis A vaccine
India
Polysaccharide Vaccine
Typhoid fever
03 medical and health sciences
0302 clinical medicine
Poverty Areas
medicine
Cluster Analysis
Humans
030212 general & internal medicine
Cluster randomised controlled trial
Typhoid Fever
Child
vaccine effectiveness
business.industry
Typhoid-Paratyphoid Vaccines
Public Health, Environmental and Occupational Health
Vi polysaccharide vaccine
General Medicine
medicine.disease
Child, Preschool
Typhoid vaccine
Herd
cluster randomized trial
Original Article
Female
business
fried egg design
Enteric fever
Clinical trial registration: ClinicalTrials.gov, NCT00125008
Demography
Subjects
Details
- Database :
- OpenAIRE
- Journal :
- International Health
- Accession number :
- edsair.doi.dedup.....1585eaadfbc42e49c481251192bd9e3c