Developing a vaccine against Sudan virus disease

Sudan virus causes Sudan virus disease, a severe infection similar to Ebola virus disease and with a case-fatality rate of about 55%.1,2 Eight known Sudan virus outbreaks have occurred since 1976, with a cumulative total of 925 cases and 460 deaths.3 The largest of those affected Uganda in 2000–01 with 425 reported cases and 224 deaths.3 Sudan virus is also responsible for a recent outbreak that affected Uganda between August, 2022, and January, 2023, causing 164 reported cases and 55 confirmed deaths.3,4 There are no approved vaccines or therapeutics against Sudan virus.5 Vaccines approved against Ebola virus do not provide cross-protection against Sudan virus because the two viruses are antigenically different.5 Therefore, the response to Sudan virus outbreaks relies mainly on key control measures such as early case identification and isolation, contact tracing and monitoring, safe burials, and community awareness of transmission risks.4,5 An effective vaccine for the protection of health-care workers or ring vaccination of contacts of cases and contacts of contacts could be an important addition to the available tools to control Sudan virus outbreaks. The study has some limitations, which were acknowledged by the authors, such as the small sample size, the absence of a control group, and the recruitment of fewer female participants. Phase 2 randomised controlled trials in Africa and USA are planned for this vaccine,7,9 and the regulatory plan is set to pursue licensure through the US Food and Drug Administration's Animal Rule unless effectiveness data become available.7 This licensure pathway will require immunobridging studies correlating the vaccine-induced protection against Sudan virus in non-human primates to the immune responses in vaccinated subjects to identify the likelihood of protection in humans.7,9,10 A licensed vaccine against Sudan virus will strengthen the preparedness and response against the next outbreak of Sudan virus disease.