Previous studies have already shown the effectiveness of one oral cholera vaccine dose in countries that had recently experienced cholera. At the time of the 2016 outbreak, Zambia had not reported a case of cholera in four years.
“According to these results, people vaccinated can be protected against cholera a few days after receiving one dose,” said Epicentre’s Dr. Francisco Luquero, one of the study’s authors. “This is important in outbreaks when we need to protect people quickly. We now know that just one dose provides adequate short-term protection both for people with recent exposure to the disease and also for those who have not been exposed to it in several years, such as people in Lusaka and much of sub-Saharan Africa.”
Cholera is a water-borne disease that causes watery diarrhea and vomiting. If left untreated, it can be fatal. The disease is most common in densely populated areas where sanitation is poor and water supplies are not safe.
In April 2016, the Zambian MOH, supported by MSF and the WHO, implemented an emergency single-dose vaccination campaign in Lusaka that targeted more than half a million people.
A global shortage of vaccines in 2016 led to the decision to provide only one dose of the cholera vaccine, allowing for more people to be protected. The second dose was delivered later that year when more vaccines became available. Effectively protecting people against cholera with a single dose of the vaccine could mean more people can be vaccinated during a large-scale emergency even when there are global vaccine shortages, such as in this case.
“While the availability of vaccines has improved in recent years, the number is still far from being sufficient to tackle the large-scale outbreaks we are currently seeing, such as those currently ongoing in the Democratic Republic of Congo or Yemen,” Luquero said. “However, we are extremely encouraged by these results which will mean more people can be protected from this potentially deadly disease.”
The results of the study for children under five are still not clear, as there were few occurrences of the disease in children in the 2016 epidemic. “It is important that future studies look at the effect of the vaccine on children under five as they are generally less protected and more vulnerable to the disease,” Luquero said.