Health workers in the Democratic Republic of the Congo are vaccinating people to help stop the spread of the Ebola virus.Credit: Olivia Acland/Reuters

The aid organization Médecins Sans Frontiéres says that the World Health Organization (WHO) is not distributing Ebola vaccine widely enough in the Democratic Republic of the Congo (DRC).

An epidemic of the virus in the DRC has sickened more than 3,100 people and killed over 2,100 since August 2018, according to the WHO. The agency, an arm of the United Nations, has been distributing the rVSV-ZEBOV vaccine in areas of the DRC where Ebola is spreading.

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The vaccine, made by Merck, is more than 97% effective, according to a preliminary analysis published in April by the WHO and DRC government researchers. Yet Médecins Sans Frontiéres (MSF, also known as Doctors without Borders) says that “only a fraction of the eligible population” in the DRC has received the vaccine — roughly 225,000 of the 600,000 people that the group estimates should have received the shot.

Health workers are among those who have been under-vaccinated, MSF says, noting that 160 have been infected with the virus. “In a hotspot of the outbreak such as Beni, almost a third of [health workers] reported they have not been vaccinated,” said Isabelle Defourny, MSF’s director of operations, who is based in Paris, in a statement on 23 September. Beni is a city in the eastern DRC.

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The MSF’s criticisms came as the WHO said it would roll out a second Ebola vaccine this October to combat the outbreak. The WHO plans to give this vaccine, made by Johnson & Johnson, to people in the eastern DRC who live in areas free of Ebola.

Ibrahima Socé Fall, the assistant director-general of WHO’s emergency response, rejects many of MSF’s claims — beginning with the group’s estimate that 600,000 people should have received the Merck vaccine.

A tough task

The WHO’s strategy has focused on vaccinating people who have come into contact with a person who has been diagnosed with Ebola, along with the contacts of those contacts, and health workers. Socé Fall argues that MSF has overestimated the number of people who should be vaccinated. The aid group based its projection on the average number of contacts per person diagnosed with Ebola — but in many cases, Socé Fall says, the contacts of people with Ebola overlap. This reduces the overall number of people who need to be immunized against the virus.

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Socé Fall also disputes MSF’s estimate that one-third of health workers haven’t been offered the vaccine. He says that no one knows the true number of health workers in the areas where Ebola is spreading, because the term includes traditional healers as well as doctors and nurses offering modern medical treatment — and others who mix both kinds of care. The WHO has struggled to find and vaccinate health workers who operate small, unregistered facilities scattered throughout the forests of the eastern DRC.

“Every day you discover people who are practicing traditional medicine, some integrate some modern medicines too,” Socé Fall says, “and there is no database of these people.” He adds that continuing violence in the eastern DRC has made it hard for WHO teams to trace and vaccinate the contacts of people with Ebola.

Nathalie Roberts, an emergency operations manager at MSF who is based in Paris, says that the WHO’s vaccination strategy no longer makes sense because tracing contacts of people with Ebola has proven so difficult. Around half of all people diagnosed with Ebola during this outbreak were not identified as contacts of the sick before they themselves became ill — and so never received the vaccine. Roberts says that Ebola responders should instead vaccinate the population widely in Beni and other areas where Ebola has spread for months.