FIELD TRIAL OF A LOCALLY PRODUCED, KILLED, ORAL CHOLERA VACCINE IN VIETNAM

Background Several studies have shown that orally administered killed cholera vaccines are safe and protective in populations at risk of cho lera in developing countries. However, these vaccines have not been ad opted for use in developing countries because of their expense and lim ited efficacy in young children. We have tested an inexpensive, killed whole-cell cholera vaccine developed and produced in Vietnam. Methods The efficacy of the vaccine was assessed in a large-scale, open field trial in people at least 1 year old residing in 22 653 households in the central coastal city of Hue. Alternate households were assigned va ccine (67 395 people; two doses per person) or no vaccine (67 058 peop le). Surveillance for cholera was conducted in all Ministry of Health facilities serving this population. Analysis was by intention to treat . Findings During an outbreak of El Tor cholera 8-10 months after vacc ination, 37 cases of cholera requiring inpatient care occurred among a ge-eligible people allocated to the vaccine group, and 92 cases among age-eligible people allocated to the no-vaccine group (protective impa ct 60% [95% CI 40-73]). Among the 51 975 people who received the compl ete two-dose vaccine regimen, the protective efficacy was 66% (46-79); in this subset, the protective efficacy was similar for children aged 1-5 years (68%) and for older people (66%). Interpretation These find ings suggest that oral killed whole-cell vaccines can confer substanti al protection against El Tor cholera in young children, who are at hig hest risk of cholera in endemic settings. An inexpensive, locally prod uced, and effective oral cholera vaccine may be within reach of the li mited healthcare budgets of poor countries with endemic cholera, if ou r findings can be replicated in a randomised double-blind trial.