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Cholera outbreak shows need for safer water, questionable role for vaccines
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With almost 274,000 patients and more than 4,700 dead, the outbreak of cholera in Haiti has demonstrated just how powerful and devastating this illness can be, according to a speaker.
Eric Mintz, MD, MPH, an epidemiologist with the CDC, said the recent outbreak demonstrates the need for enhanced prevention strategies to address longstanding deficiencies in access to safe drinking water and improved facilities for sanitation and hygiene.
A recent study projected that if there were a 1% decrease in the consumption of contaminated water, 105,000 cases of cholera and 1,500 deaths could potentially be avoided in the coming year. In addition, 63,000 cases and 900 deaths could be averted if only 10% of the population were vaccinated. The distribution of antibiotics to those with severe dehydration and just half of those with moderate dehydration would also avoid thousands of deaths, according to the researchers.
Although the disease no longer poses a threat to countries with minimum standards of hygiene, it remains a challenge to countries where access to safe drinking water and adequate sanitation cannot be guaranteed. Almost every developing country faces cholera outbreaks or the threat of a cholera epidemic, Mintz said, citing modern epidemics in Peru, Goma (Zaire) and Zimbabwe.
He said increasing access to safe drinking water is paramount, noting that Latin America eliminated cholera without access to a vaccine just by providing better access to safer water. Concurrent declines in the incidence of other enteric infections, such as typhoid fever and hepatitis A, and in overall infant and child mortality were documented in some countries.
Currently, WHO officials recommend that in countries where cholera is endemic, cholera vaccines “should be used in conjunction with other prevention and control strategies,” including stepped up water sanitation and hand hygiene efforts. The role of cholera vaccines in outbreak control is less clear. WHO maintains that the mainstay of control measures to be implemented during ongoing epidemics should remain: 1) providing appropriate treatment to people with cholera; 2) implementing interventions to improve water and sanitation; and 3) mobilizing communities. Also, pre-emptive vaccination should be considered by local health authorities to help prevent potential outbreaks or the spread of current outbreaks to new areas, and that during an ongoing epidemic, reactive vaccination could be considered by local health authorities as an additional control measure, depending on the local infrastructure, and after a thorough investigation of the current and historical epidemiologic situation, and clear identification of areas to be targeted, Mintz told Infectious Diseases in Children.
The history of cholera vaccine development has been long, but has yet to yield a product ideally suited for use in epidemic control, he said. Currently available vaccines require two doses at least 1 week apart and provide incomplete protection of relatively short duration. A single-dose, live oral cholera vaccine was introduced in the 1980s that was 62% to 100% effective; however, field testing in Indonesia between 1993 and 1996 proved inconclusive because of a lack of cholera cases in the control group, and that vaccine was discontinued in 2008.
Two killed oral vaccines are currently available (only one is WHO pre-qualified), but problems such as cost, limited duration of protection, identifying high-risk population targets and strategies to reach them, and the difficulty in accurately predicting when and where cholera epidemics will strike next are limiting the utility of these vaccines in developing countries.
For more information:
- Mintz E. #25628.
Disclosure: Dr. Mintz reports no relevant financial disclosures.