Oral killed cholera vaccines for preventing cholera

Abstract

Background Cholera causes acute watery diarrhoea and death if not properly treated. Outbreaks occur in areas with poor sanitation, including refugee camps. Several vaccines have been developed and tested over the last 50 years. This is an update of a Cochrane review, originally published in 1998, which explored the effects of all vaccines for preventing cholera. This review examines oral vaccines made from killed bacteria. Objectives To assess the effectiveness and safety of the available World Health Organization (WHO)‐prequalified oral killed cholera vaccines among children and adults. Search methods We searched the Cochrane Infectious Diseases Group Specialized Register; CENTRAL, MEDLINE; Embase; LILACS; and two trials registers (February 2023). Selection criteria We included randomized controlled trials (RCTs), including cluster‐RCTs. There were no restrictions on the age and sex of the participants or the setting of the study. We considered any available WHO‐prequalified oral killed cholera vaccine as an intervention. The control group was given a placebo, another vaccine, or no vaccine. The outcomes were related to vaccine effectiveness and safety. We included articles published in English only. Data collection and analysis Two review authors independently applied the inclusion criteria and extracted data from included studies. We assessed the risk of bias using the Cochrane ROB 1 assessment tool. We used the generic inverse variance and a random‐effects model meta‐analysis to estimate the pooled effect of the interventions. We assessed the certainty of the evidence using the GRADE approach. For vaccine effectiveness (VE), we converted the overall risk ratio (RR) to vaccine effectiveness using the formula: VE = (1 ‐ RR) x 100%. Main results Five RCTs, reported in 12 records, with 462,754 participants, met the inclusion criteria. We identified trials on whole‐cell plus recombinant vaccine (WC‐rBS vaccine (Dukoral)) from Peru and trials on bivalent whole‐cell vaccine (BivWC (Shanchol)) vaccine from India and Bangladesh. We did not identify any trials on other BivWC vaccines (Euvichol/Euvichol‐Plus), or Hillchol. Two doses of Dukoral with or without a booster dose reduces cases of cholera at two‐year follow‐up in a general population of children and adults, and at five‐month follow‐up in an adult male population (overall VE 76%; RR 0.24, 95% confidence interval (CI) 0.08 to 0.65; 2 trials, 16,423 participants; high‐certainty evidence). Two doses of Shanchol reduces cases of cholera at one‐year follow‐up (overall VE 37%; RR 0.63, 95% CI 0.47 to 0.85; 2 trials, 241,631 participants; high‐certainty evidence), at two‐year follow‐up (overall VE 64%; RR 0.36, 95% CI 0.16 to 0.81; 2 trials, 168,540 participants; moderate‐certainty evidence), and at five‐year follow‐up (overall VE 80%; RR 0.20, 95% CI ...