MONDAY, March 21 (HealthDay News) -- The currently available oral cholera vaccine may prevent 50 to 60 percent of cholera episodes in the first two years after vaccination, but its effectiveness is unlikely to last beyond three years, according to a review published in the Cochrane Database of Systemic Reviews.
David Sinclair, M.D., of the Liverpool School of Tropical Medicine in the United Kingdom, and colleagues reviewed 40 studies to assess the effectiveness and safety of oral cholera vaccines in preventing cases of cholera and deaths from cholera. The review included seven large efficacy studies, four small artificial challenge studies, and 29 safety trials. The main outcome measure was vaccine protective efficacy.
The researchers found overall vaccine efficacy of killed whole cell vaccine to be 52 percent in the first year and 62 percent in the second year. In children younger than 5 years, the protective efficacy was 38 percent; whereas, among older children and adults, it was 66 percent. There was no efficacy data available for the current vaccine formulations beyond two years, but results from older trials suggested that it is unlikely to last longer than three years. There was no clinically significant increase in adverse events with the vaccine compared to placebo.
"The impact and cost-effectiveness of adopting oral cholera vaccines into the routine vaccination schedule of endemic countries will depend on the prevalence of cholera, the frequency of epidemics, and access to basic services providing rapid rehydration therapy," the authors write.