Oral cholera vaccines are now frequently used in cholera prevention and control. However, gaps in evidence of its efficacy and effectiveness have hindered its widespread use. Researchers performed a systematic review and meta-analysis to investigate the efficacy and direct effectiveness of the cholera vaccine.
Previous studies on effectiveness and efficacy of the oral cholera vaccines have provided a wide range of estimates. Considering its common use today, it is necessary to provide an update on the current evidence to help decision-makers assess the vaccine’s use in the population. Qifang Bi from the Department of Epidemiology at the Johns Hopkins Bloomberg School of Public Health and colleagues published their findings in The Lancet.
They extracted data from seven clinical trials, including 695 patients with cholera, and six observational studies, including 217 patients with cholera. Two-dose regimens were presented in 9 of the included studies, one-dose regimens were presented in 2 studies, and three-dose regimens were presented in the remaining 2 studies. The primary endpoints of this review were vaccine efficacy (estimated by randomized clinical trials) and vaccine effectiveness (estimated by observational studies).
The average two-dose regimen efficacy from the clinical trials was 58%, and the average two-dose regimen vaccine effectiveness was 76%. The single one-dose regimen observational study provided an effectiveness of 69% and the clinical trial estimated a vaccine efficacy of 40%. Both one-dose regimen studies only provided short-term estimates at two months and six months. The two remaining studies investigated the efficacy of a three-dose regimen.
Researchers identified different vaccine scheduling strategies. In one study, three doses were administered with a six-week interval in between each oral vaccine. The researchers for this study did not identify a significant difference between the efficacy of the two-dose and three-dose regimen. Furthermore, in the second study, a third dose was administered as a booster 10 months after the primary two-dose regimen. The efficacy after two years was 82%.
In conclusion, the oral cholera vaccine does provide protection against cholera and is an important tool in cholera prevention. The standard two-dose regimen offers at least three years of protection. The one-dose regimen provides shorter-term protection, which has important implications for outbreak management or when vaccine supply is limited.
Standard cholera control and prevention also includes established water, sanitation, and hygiene interventions, as well as proper surveillance and case management. In vulnerable populations, as water, sanitation, and healthcare infrastructure improve, the cholera vaccine offers a safe defense against the cholera bacteria.
Written by Jessica Caporuscio, PharmD
Reference: Bi Q, Ferreras E, Pezzoli L, et al. Protection against cholera from killed whole-cell oral cholera vaccines: a systematic review and meta-analysis. Lancet Infect Dis. 2017.
