The use of killed oral cholera vaccines can confer moderate levels of direct protection to vaccines.
Decisions to use these can depend on whether the vaccines also provide indirect (herd) protection when high levels of vaccine coverage are attained.
Dr John Clemens and colleagues reanalyzed data from a field trial in Bangladesh to ascertain whether there is evidence of indirect protection from killed oral cholera vaccines.
|Vaccine coverage of the targeted population ranged from 4% to 65%|
The investigators analyzed the first year of surveillance data from a placebo-controlled trial.
The investigative team assessed B subunit-killed whole-cell and killed whole-cell-only oral cholera vaccines in children and adult women.
The team calculated whether there was an inverse trend for the relation between the level of vaccine coverage in a residential cluster and the incidence of cholera in individual vaccine recipients.
The investigators compared this to placebo recipients residing in the cluster after controlling for potential confounding variables.
The team reported that vaccine coverage of the targeted population ranged from 4% to 65%.
The research team found that incidence rates of cholera among placebo recipients were inversely related to levels of vaccine coverage.
The receipt of vaccine by an individual and the level of vaccine coverage of the individual's cluster were independently related to a reduced risk of cholera.
After adjustment for the level of vaccine coverage of the cluster, the investigators observed that vaccine protective efficacy remained significant.
Dr Clemens' team concluded, “In addition to providing direct protection to vaccine recipients, killed oral cholera vaccines confer herd protection to neighbouring non-vaccinated individuals.”
“Use of these vaccines could have a major effect on the burden of cholera in endemic settings.”