Efficacy of Killed Whole-Cell Oral Cholera Vaccine Examined

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Efficacy estimates similar during the 2 years after vaccination; efficacy reduced in third, fourth year
Efficacy estimates similar during the 2 years after vaccination; efficacy reduced in third, fourth year

HealthDay News — Two doses of killed whole-cell oral cholera vaccine (kOCV) are efficacious for protecting against cholera for at least 2 years after vaccination, according to a review published online July 17 in The Lancet Infectious Diseases.

Qifang Bi, M.H.S., from the Johns Hopkins Bloomberg School of Public Health in Baltimore, and colleagues conducted a systematic review and meta-analysis to estimate kOCV efficacy and effectiveness. Data from seven trials, with 695 patients with cholera, and six observational studies, with 217 patients with cholera, were included. 

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The researchers found that the average 2-dose efficacy was 58% and effectiveness was 76%. However, in children younger than 5 years, the average 2-dose efficacy was lower than in those aged 5 years or older (30 versus 64%; P<0.0001). During the 2 years after vaccination the 2-dose efficacy estimates were similar, with estimates of 56 and 59% in the first and second year, respectively. In the third and fourth year, the efficacy was reduced to 39 and 26%, respectively.

"In conclusion, kOCVs are effective in reducing the risk of cholera," the authors write. "More work is needed to understand how and when to best use existing vaccines and to design new and more effective ones."

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