Uganda’s health ministry, with support from the World Health Organization (WHO) and its partners, today launched a vaccine trial against the Ebola Sudan virus, the first to assess the clinical efficacy of a vaccine specific to the Ebola Sudan virus.
Tedros Adhanom Ghebreyesus, PhD, WHO director-general, on X today said the trial will enroll contacts of sick people as well as contacts of contacts, known as a ring vaccination strategy.
“This vaccination trial was initiated with record speed, only three days since the outbreak was declared, while ensuring full compliance with international and national regulatory and ethical requirements,” he said, adding that the WHO will continue supporting Uganda’s government in its response to the outbreak.
In a January 31 statement, the WHO said the first 2,160 doses of the candidate vaccine, as well as treatments, were already prepositioned in Kampala as part of outbreak preparedness. Uganda has experienced five earlier Ebola Sudan outbreaks.
Uganda declared the outbreak on January 30. In a February 1 outbreak notice, the WHO revealed more details, including that that male nurse’s fever symptoms began between January 20 and January 21, and he had sought care from a traditional healer, as well as multiple health facilities before he was hospitalized after his condition worsened.
So far, 45 contacts have been identified, including 34 health workers and 11 family members.
Initial sequencing suggests no links to 2022 outbreak
In another new development, a scientist from Uganda’s Central Public Health Laboratory shared preliminary sequencing findings on Virological, an online hub for prepublication data designed to assist with public health activities and research. Stephen Kanyerezi, MSc, a bioinformatics scientist with Makerere University, wrote that sequencing was conducted the same day samples were collected on the day the patient died, which was January 29.
Phylogenetic analysis suggest that 2025 strain does not cluster with Ebola Sudan sequences from the country’s last outbreak in 2022. However, it shows a strong relationship to sequences from the 2012 Luwero lineage, suggesting a shared epidemiologic source, possibly a common zoonotic reservoir, or an independent spillover event.
“These findings refute the possibility of sustained human-to-human transmission from the 2022 outbreak and raise questions regarding the current outbreak’s source and transmission dynamics,” the group said.
