One-dose cholera vaccine gives 90 per cent protection
- Researchers assessed effectiveness of single-dose cholera vaccine in Zambia
- Its effectiveness was 90 per cent in setting with no outbreak for four years
- Expert calls for further assessment of how long protection effect lasts
According to researchers, a shortage in the global stockpile of cholera vaccines meant that single-dose oral vaccination was necessary to tackle an outbreak in Lusaka, Zambia, in February 2016.
The emergency vaccination campaign was implemented in April 2016, targeting more than 500,000 people in Lusaka’s overcrowded township areas.
Francisco Luquero, co-author of the study and an expert in preventable diseases at the France-based Epicentre, the research arm of the Médecins Sans Frontières (MSF) or Doctors without Borders, says that studies have already proven that one dose of oral cholera vaccine works — but those studies were conducted in countries that had recently experienced cholera.
The 2016 outbreak happened when Zambia had not reported a case of cholera in four years.
“Our results show that people vaccinated can be protected against cholera a few days after receiving one dose.”
To determine the effectiveness of the single-dose cholera vaccine, the researchers enrolled 66 patients with confirmed cholera and 330 people without the disease who were neighbours of the patients.
According to the study, published last month (8 February) in the New England Journal of Medicine, the effectiveness of the single dose vaccination was about 90 per cent.
“Our results show that people vaccinated can be protected against cholera a few days after receiving one dose, which is important in outbreaks because we need to protect people quickly,” says Luquero.
Oral cholera vaccines have been used in past years to successfully prevent outbreaks in complex emergencies, to curb epidemics, or to reduce the disease burden in countries where cholera is endemic but vaccines are in short supply, according to MSF.
The Lusaka outbreak ended quickly after the implementation of the vaccination campaign, which limited the number of cases recruited for the study, Luquero explains. The Ministry of Health offered a second vaccine eight months later, in December 2016.
The WHO estimates that globally, cholera infects between one and four million people a year, resulting in 21,000-143,000 deaths, with countries in Sub-Saharan Africa at increased risk.
“This is an important study because it suggests that the world could face the challenges of cholera outbreaks with a single dose,” says Roma Chilengi, chief scientific officer at the Centre for Infectious Disease Research in Zambia. A single-dose vaccine is cheaper and could help countries with limited financial ability to control the disease, he added.
However, “it would be helpful to be clear about the potential duration of the protection the single dose offers,” Chilengi tells SciDev.Net.
This piece was produced by SciDev.Net’s Sub-Saharan Africa English desk.