Cholera is an acute gastroenteritis caused by Vibrio cholerae. Infection causes profuse watery diarrhoea, and up to 40% of patients die if untreated. Cholera was a major cause of death in many countries in the past; epidemics are now less common, but cholera remains an important cause of death in developing countries, especially in Africa.
Vaccination against cholera was first tested in the nineteenth century and may play a role in controlling epidemics. Injected (parenteral) whole cell vaccines were used in the 1960s and 1970s, but they went out of favour as their efficacy was thought to be low and short-lived, and associated with a high rate of adverse effects. This review summarizes the evidence for effectiveness of injected cholera vaccines. A separate Cochrane Review describes trials with oral cholera vaccines, which were introduced more recently and are used currently.
Sixteen trials, involving over one million adults, children, and infants, were included. Injected cholera vaccines reduced the risk of death from cholera and the risk of contracting cholera at 12 months. Significant protection lasted for two years. Injected cholera vaccines had more systemic and local adverse effects than placebo, but these adverse effects were relatively well tolerated and were not severe or life-threatening.
The authors conclude that injected cholera vaccines appear to be relatively safe and more effective than usually realized. However, they are not currently available and therefore cannot be recommended for use. This review provides a solid background of evidence for the effects of cholera injected vaccines, against which to compare the effects of oral vaccines.