New cholera vaccine shows promise

The success of the first mass immunisation campaign against cholera in Mozambique's port city of Beira has prompted calls for greater access to the oral vaccine. From December 2003 to January 2004 about 50,000 residents in the poor district of Esturro received two successive weekly doses of the oral cholera vaccine, rBS-WC. Researchers then assessed the effectiveness of the vaccine during an outbreak in Beira between January and May 2004 and found that it was highly effective, protecting between 78 and 84 percent of the recipients from cholera for six months, with 50 percent being protected for three years. Needle-administered cholera vaccines have generally provided about 50 percent protection for just two months. None of the 20 people who died during the outbreak had received the vaccine. Cholera is endemic in Mozambique and during the rainy season the cities of Maputo and Beira are usually worst affected. Researchers noted that while similar studies carried out in Bangladesh and Peru had shown promise, the Mozambique trial was the first to target a population with high HIV prevalence - around 30 percent. They inferred from their findings that the vaccine could be effective in people with the HI virus. The high cost of the vaccine - US $2 per dose - and a lack of evidence that it would work in people whose immune systems were compromised by HIV had previously deterred researchers from using the new vaccine in sub-Saharan Africa. "The oral cholera vaccine could be an important tool for Mozambique in the next two to three years, particularly in areas where populations are at high risk of cholera, and where there is a high prevalence of people living with HIV/AIDS. It can give these people new hope," coordinator of the trials Marcelino Lucas told IRIN. However, Lucas pointed out the study had not included HIV testing and further research and monitoring was needed to assess the safety of the vaccine among HIV-positive people. Although cholera awareness campaigns are instrumental in preventing the spread of the disease, they have had a limited impact because of poor access to proper sanitation facilities and clean water. The cholera bacterium, spread mainly through contaminated water or food, causes severe diarrhoea and dehydration. Epidemics are linked to poor hygiene, overcrowding, inadequate sanitation and unsafe water. Despite government efforts, around 74 percent of Mozambique's rural population does not have access to safe drinking water; access to potable water in urban areas is slightly better, but more than half the people living in towns and cities are without adequate sanitation. Lucas said financing a sustainable supply of the vaccine was critical, as the success of oral vaccines in Mozambique meant that much-needed resources, previously spent on caring for the sick, could instead be used for strengthening cholera prevention measures.