A single dose of the inactivated whole-cell oral cholera vaccine (OCV) may protect individuals vaccinated at ages 5 years and beyond, the protective effect remaining sustained for at least 2 years, according to a study published inThe Lancet Infectious Diseases.
A double-blinded study included individuals aged >1 year who were randomly assigned to receive either a single dose of inactivated OCV (n=102,552) or oral placebo (n=102,148). Researchers assessed the protective efficacy of the OCV during the first 6 months of follow-up and evaluated initial episodes of all types of cholera 7–730 days after vaccination among participants who had ingested a full dose.
During the 2-year follow-up, the first episodes of cholera were detected in 109 vaccine recipients vs 178 placebo recipients (P<.0001), whereas severe dehydration was seen in 46 vaccine recipients vs 92 placebo recipients (P=.0001). The overall incidence of initial cholera episodes was 0.22 (95% CI, 0.18-0.27) per 100,000 person-days vs 0.36 (95% Cl, 0.31-0.42) per 100,000 person-days in vaccine vs placebo recipients (adjusted protective efficacy, 39%; 95% CI, 23-52). The overall incidence of severe cholera was 0.09 (95% CI, 0.07-0.12) per 100,000 person-days vs 0.19 (95% CI, 0.15-0.23; adjusted protective efficacy, 50%, 95% CI,29-65). The vaccine did not show protection against all cholera episodes (protective efficacy, −13%; 95% CI, −68 to 25) or severe cholera episodes (−44%; 95% CI, −220 to 35) in children aged <5 years. Sustained protection for cholera throughout the 2-year follow-up was seen in people aged 5 years and above.
“Completing a two-dose regimen should not deter deployment of OCV, because older children and adults will be protected for at least 2 years by a single dose in populations with endemic cholera. Further evaluations of either a single-dose or two-dose regimen of the inactivated whole-cell OCV in settings without endemic cholera should be investigated,” the authors said.
