Oral Cholera Vaccines: Efficacy and Effectiveness in Cholera Prevention
Introduction to Oral Cholera Vaccines
Oral cholera vaccines are increasingly utilized in efforts to prevent and control cholera outbreaks. Nonetheless, gaps in the evidence regarding their efficacy and effectiveness have limited their broader application. To address this, researchers undertook a systematic review and meta-analysis to evaluate the efficacy and direct effectiveness of the cholera vaccine.
Previous Research and The Need for Updated Evidence
Earlier studies on the effectiveness and efficacy of oral cholera vaccines have yielded a diverse range of estimates. Given the vaccine’s widespread use today, it is crucial to update the current evidence to assist decision-makers in evaluating its application within populations.
Research Findings
Qifang Bi, along with colleagues from the Department of Epidemiology at the Johns Hopkins Bloomberg School of Public Health, published their findings in The Lancet. They analyzed data from seven clinical trials involving 695 cholera patients, alongside six observational studies with 217 cholera patients. The studies included various dosing regimens: nine studies featured two-dose regimens, two studies focused on one-dose regimens, and the remaining two investigated three-dose regimens.
Primary Endpoints of the Review
The primary endpoints of this review were vaccine efficacy, estimated through randomized clinical trials, and vaccine effectiveness, assessed via observational studies. The average efficacy for the two-dose regimen, based on clinical trials, was found to be 58%, while the average effectiveness for the same regimen, based on observational studies, was reported at 76%.
For the one-dose regimen, an observational study indicated an effectiveness of 69%, whereas a clinical trial estimated a vaccine efficacy of 40%. It is important to note that both one-dose regimen studies only provided short-term estimates, evaluated at two and six months.
Exploration of Three-Dose Regimens
The two remaining studies focused on the efficacy of a three-dose regimen. In one study, three doses were administered with a six-week interval between each dose. Here, researchers found no significant difference in efficacy between the two-dose and three-dose regimens. The second study administered a booster dose ten months after the primary two-dose regimen, reporting an efficacy of 82% after two years.
Conclusions on Vaccine Use
In conclusion, the oral cholera vaccine does confer protection against cholera and represents a vital tool for its prevention. The standard two-dose regimen offers at least three years of protection, while the one-dose regimen provides shorter-term protection, which is particularly relevant for outbreak management or when vaccine supplies are constrained.
Complementary Cholera Control Measures
Standard cholera control and prevention strategies also encompass established water, sanitation, and hygiene interventions, along with effective surveillance and case management. In vulnerable populations, as improvements in water, sanitation, and healthcare infrastructure occur, the cholera vaccine serves as a safe defense against cholera bacteria.
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.