Single dose of oral cholera vaccine effective for at least 36 months
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Key takeaways:
- Effectiveness of the vaccine was 52.7% and 44.7% at 12 to 17 and 24 to 36 months after vaccination, respectively.
- Effectiveness among children younger than 5 years dropped after the third year.
A single dose of Eubiologics’ oral cholera vaccine provided significant protection against cholera for at least 36 months, according to data from a vaccination campaign organized in a cholera-endemic city in Africa.
“Globally, there is a shortage of cholera vaccine, with only 33 million of the 72 million requested doses delivered to countries. The International Coordinating Group, the WHO-backed organization that manages the global stockpile of oral cholera vaccines, recommended the use of a single dose, rather than the standard two-dose regimen in emergency vaccination, because of insufficient production capacity,” Espoir Bwenge Malembaka, MD, PhD,, postdoctoral fellow in the Department of Epidemiology at Johns Hopkins University, told Healio.
“There is, however, a dearth of evidence on the strength and duration of protection conferred by a single dose of oral cholera vaccines, particularly in children who are younger than 5 years at vaccination,” he said.
According to Malembaka, the city of Uvira in eastern Democratic Republic of Congo (DRC) is one of the key cholera hotspots in the country and has reported cholera cases throughout the year with one to two seasonal peaks.
Malembaka explained that a mass cholera vaccination campaign using the oral Euvichol-Plus vaccine was organized in the city in 2020, with the majority of vaccinated people reporting that they received one dose of the vaccine.
“Uvira offered a unique opportunity to understand how well and for how long a single dose of the Euvichol-plus vaccine, the only oral cholera vaccine currently available in the global stockpile, can protect the population,” Malembaka said.
The researchers conducted a matched case-control study during which they recruited patients with medically attended confirmed cholera at either of Uriva’s two cholera treatment facilities. The control group consisted of age-matched, sex-matched and neighborhood-matched community individuals who were recruited during two distinct periods — Oct. 14, 2021, to March 10, 2022, (12 to 17 months after vaccination), and Nov. 21, 2022, to Oct. 18, 2023 (24 to 36 months after vaccination).
A total of 658 patients with confirmed cholera and 2,274 matched individuals for the control group were included in the study. Overall, the study demonstrated that the adjusted single-dose vaccine effectiveness was 52.7% (95% CI, 31.4-67.4) 12 to 17 months after vaccination and 44.7% (95% CI, 24.8-59.4) 24 to 36 months after vaccination.
The study also showed that protection in the first 12 to 17 months after vaccination in children aged younger than 5 years was similar to that in older patients. However, this protection “remarkably dropped,” according to Malembaka, after the third year (32.9%; 95% CI, –30.7 to 65.5).
“This is the first study that measures the effectiveness of a single dose of an oral cholera vaccine in Africa for up to 3 years after vaccination,” Malembaka said. “We showed that the current recommendation of using a single dose of cholera vaccine in emergency contexts where cholera is endemic, like in eastern DRC, can provide a similar level of protection against clinical cholera as the standard two-dose regimen in the general population, up to 3 years after vaccination.”
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