Weapons of mass vaccination

This article first appeared in The Lancet

Cholera fighters might soon have a new weapon in their arsenal - an oral vaccine that is being tested in a demonstration project in Beira, Mozambique. WHO has joined forces with Médecins Sans Frontières (MSF), Epicentre (a non-profit organisation created by MSF), the Mozambique Ministry of Health, and the International Vaccine Institute to implement a mass - vaccination campaign, which finished at the end of January 2004.

Although the vaccine has been around for at least a decade, this is the first time it has ever been tested on such a large scale - MSF expected to vaccinate about 50,000 adults and children. The vaccine is made of killed whole-cell Vibrio cholerae O1 with purified cholera toxin. Two doses, given a maximum of one week apart, should confer at least one year's protection against the disease.

Logistical problems of transportation and safe water needed for each dose, coupled with financial constraints (the vaccine is currently on the market for about US$5), partly explain why the vaccine was not used greatly.

Claire-Lise Chaignat, coordinator of WHO's Global Task Force on Cholera Control, told TLID that in addition to these factors WHO has never considered cholera vaccine for disease control because we've always said that if you have proper sanitation and access to safe water you've got the problem solved, but we realise now that it is not that easy.

The campaign was prompted by the conclusion from a meeting of experts in Geneva last year that a new approach for cholera control was needed urgently. Mozambique has been severely affected by cholera epidemics, and the health system has been able only to deal with outbreaks rather than prevent their occurrence. The vaccination project in Beira is the first demonstration of the approach, and will be followed by two more projects in other areas where cholera is endemic.

With the initial vaccination over, the next set of analyses will be of the feasibility and acceptability of the project and vaccine coverage, which will then be followed by a case-control study to assess the efficiency of protection against the bacterium that causes cholera.

So what does this mean for cholera control on a large scale? Better food hygiene, safer water, and health education are still important and should not be overlooked.

Chaignat stresses that the vaccine will not be appropriate for all areas, but could be a highly effective strategy for high-risk populations living in areas prone to frequent epidemics and where it is difficult to improve water access and sanitation. Philippe Cavailler, an epidemiologist at Epicentre, also believes that the price of the vaccine will need to be reduced to make its use a viable strategy.