Abstract
Although measuring vaccine efficacy through the conventional phase III study design, randomized, double-blinded controlled trial serves as the “gold standard”, effectiveness studies, conducted in the context of a public health program, seek to broaden the understanding of the impact of a vaccine in a real world setting including both individual and population level impacts. Cholera is an acute diarrheal infection caused by the ingestion of food or water contaminated with the bacterium Vibrio cholerae. Since the 1980s, either killed or live oral cholera vaccines (OCVs) have been developed and efficacy and effectiveness studies have been conducted on OCV. Although the results of OCV effectiveness studies sometimes showed outliers, the tendency seen is for effectiveness of the vaccine used in public health settings to be somewhat higher than estimated in randomized controlled trials due to the influence of indirect herd protection. Efficacy and Effectiveness studies both generate important information about the vaccine performance characteristics and its impact when used in real world populations at risk for the disease.
Highlights
A matched case-control study was conducted between May and October 2012 to evaluate the short-term effectiveness of two doses of ShancholTM following a reactive oral cholera vaccines (OCVs) campaign conducted as a part of integrated cholera outbreak control interventions [54]
The results show that even with moderate vaccine coverage, the incidence of severely dehydrating cholera was reduced by OCV in the study population, irrespective of vaccination status, when vaccine was administered via routine government services in a densely populated urban setting [63]
Across numerous efficacy and effectiveness studies of multiple formulation variations including killed and live whole cell oral vaccines, it is clear that oral cholera vaccines have the potential for high impact and their use can be adapted to numerous settings
Summary
Vaccine efficacy and effectiveness are generally calculated using a similar mathematical formula that is 1 minus some measure of relative risk (RR) in the vaccinated group compared with the unvaccinated group: Percentage vaccine efficacy/effectiveness. Measuring vaccine efficacy through the conventional design of phase. III randomized, double-blind, controlled clinical trial serves as the “gold standard” method for evaluating vaccines in a way that both preserves the rights of human participants and safeguards against bias [2]. Despite these strengths, efficacy trials which intentionally select ideal subjects (excluding individuals who cause variation), administer vaccine in highly structured settings, and rigorously follow subjects and outcomes can be imperfect in predicting the performance of a vaccine when it is implemented among a diverse population in routine public health practice [3]. We would like to review this history and understand how efficacy and effectiveness studies contributed to the implementation of OCV as a public health tool
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