Vaccines Could Limit The Impact Of Cholera; Mozambique Mass Campaign Tests Theory

The vaccine itself has been available for ten years, but this is the first time it has been used so broadly to minimize the devastation of a cholera outbreak. It is also the first time that WHO has considered the use of the oral cholera vaccine as part of an overall strategy to control the disease.

In recent years, the number of reported cholera cases worldwide has varied between 110 000 and 200 000 cases per year. Officially 5000 deaths occur each year. In fact, WHO estimates that the true number is probably significantly higher, due to under-reporting of cases and gaps in surveillance.

The mass vaccination project is being conducted in the Mozambique town of Beira, a community with particularly high levels of cholera 1. In 1999, the country reported 45 000 cholera cases, and Beira alone has had between 3880 and 4880 cases per year over the last three years. The vaccination campaign will finish by the end of January 2004, with about 50 000 people vaccinated, and the first results of this mass vaccination will be obtained within a year.

Cholera is mainly contracted through consumption of food or water contaminated with the bacterium Vibrio cholerae. Epidemics are linked to poor hygiene, overcrowding, inadequate sanitation and unsafe water. Current responses to cholera outbreaks are generally focused on providing care to the sick and providing safe water. While this can prevent many deaths, the lack of strong preventative measures means the disease is still a major public health problem in approximately 50 resource-poor countries.

Two types of safe and effective Oral Cholera Vaccines (OCVs) currently exist. The first vaccine consists of killed whole-cell V.cholerae 01 with purified cholera toxin. After two doses in two consecutive weeks, patients have high protection lasting for at least one year. The second vaccine consists of a single dose of attenuated live genetically modified V.cholerae 01 strain. It is the first one that is currently being used in Mozambique. The vaccine for the trial has been donated by the Swedish Biological Laboratory (SBL). In addition, the International Federation of Football Association (FIFA) has provided funds to support the cost of the trial. Though it is unlikely cholera will ever be eliminated by implementing traditional prevention strategies together with OCVs, there is now greater potential to significantly decrease the disease’s incidence in high risk populations. Many lives will certainly be saved, but perhaps even more importantly, the public health system may soon have another tool at its disposal to fight cholera.

1. Beira is the second largest city in Mozambique with a population of 500 000. It is located on the coast north of Maputo in the centre of Mozambique in Sofala Province.