First participant vaccinated in Congo's Tumaini Ebola vaccine trial

The Phase 2/3 Tumaini trial began enrolling participants in Bunia, in Ituri province, on 23 October. Doctors Without Borders said the first participant was vaccinated on 26 October. Its research arm, Epicentre, is a partner in the study. Tumaini means hope in Swahili.

The trial uses an adaptive platform designed to test several vaccine candidates at once. It is a ring vaccination study: it vaccinates people who had contact in the previous 21 days with someone newly confirmed to have Bundibugyo disease, not a general population. Each participant is randomly assigned to receive either a vaccine candidate or standard care on the first day, then the other on day 29, according to the trial design described by HNGN. The design includes pregnant women and children aged 12 and older. Children as young as 1 are eligible for the Ervebo arm.

Participants are initially receiving Ervebo, the vaccine licensed against the Zaire strain of Ebola. Nobody knows whether Ervebo protects against Bundibugyo. The WHO has stressed that testing Ervebo is not evidence that it works against the strain; laboratory studies cited by its vaccine advisers showed only a low level of cross-reacting antibodies. That makes the trial the first real test of whether vaccination can help control this outbreak.

Why Bundibugyo is different

Bundibugyo is a different Ebola species from Zaire. Ervebo and the approved antibody treatments were built for Zaire. No approved vaccine or treatment exists for Bundibugyo virus, and health workers treat patients based on their symptoms, Medical Daily reported. WHO declared the outbreak a public health emergency of international concern in May.

The toll

Africa CDC data released on Monday counted 10,444 confirmed cases and 5,376 deaths, including 5,372 in Congo and two each in Kenya and Uganda. The agency put the fatality rate above 50 percent. The U.S. CDC calls the outbreak the second-largest Ebola outbreak on record, behind the 2014 to 2016 West Africa epidemic, which caused about 28,600 cases and more than 11,000 deaths.

Agencies' totals differ because of reporting dates and scope. The European Centre for Disease Prevention and Control reported 10,141 confirmed cases and 4,928 deaths in Congo through 26 October. The U.S. CDC tallied 10,305 cases and 4,996 deaths across all affected countries as of 28 October. Africa CDC Director-General Jean Kaseya separately gave 10,172 cases, 4,932 deaths and a case fatality rate of 48.5 percent. Congo's own count was 5,458 confirmed cases and 2,606 deaths as of 21 August, so both totals roughly doubled in about ten weeks.

About 80 percent of new cases are emerging outside the chains of contacts responders are monitoring, according to Africa CDC. WHO and Africa CDC response data show 2,705 confirmed cases among children aged 17 and younger, including 1,345 under five. Save the Children said the case fatality rate among under-fives stands at 72 percent.

What happens next

Two experimental Bundibugyo vaccines are expected to join the trial after regulatory approvals and WHO recommendations. They are ChAdOx1 BDBV from the University of Oxford and mRNA-1469 from Moderna. The Oxford vaccine has been in a Phase 1 trial since July, and the Moderna candidate in Phase 1 in Canada since August. Both are still at the safety stage, which means a proven countermeasure for this strain is months or longer away, according to HNGN.

WHO Director-General Tedros Adhanom Ghebreyesus said the trial will show whether any of the vaccine candidates designed for Bundibugyo work. The first candidate being tested is Ervebo, to see whether protection against Zaire extends to Bundibugyo, HNGN reported.