Ebola: Already More than 2,000 People Included in the PREVAC Immunization Trial

Science

The Partnership for Research on Ebola VACcination (PREVAC) immunization study began one year ago, at a time when the Ebola virus was re-emerging in the Democratic Republic of the Congo. Thanks to more than 2,000 adults and children who have already been included in the study in Guinea and Liberia, this international clinical trial is evaluating the safety and immunogenicity of two potential vaccines against the Ebola virus. The results will be decisive in preventing a new epidemic.

Four years ago, the most devastating and deadly Ebola epidemic to date broke out in Guinea, Sierra Leone, and Liberia. The WHO declared an international state of emergency. The epidemic ended in mid-2016, but it left devastated populations in its wake, with nearly 29,000 sick people and 11,000 deaths on record. The lack of preventive or curative drugs, coupled with considerable morbidity-mortality, led the international scientific community to take action towards treatment and immunization. In France, the Research and Action targeting emerging infectious diseases (REACTing) consortium coordinated by Inserm managed the initiatives of the French teams researching Ebola.

The PREVAC project is designed to evaluate three immunization strategies that include different potential vaccines against the Ebola virus. This clinical trial, which is being carried out in Guinea, Liberia, Sierra Leone, and Mali, will measure the speed, intensity, and duration of the immune system reactions generated by these vaccines, as well as the safety and tolerance of the products administered, in adults and in children over the age of one year.

The PREVAC Consortium

Launched in 2017, the Partnership for Research on Ebola VACcination (PREVAC) trial is supported by an international consortium that includes Inserm, the American NIH (National Institutes of Health), the LSHTM (London School of Hygiene and Tropical Medicine), and the health authorities in the four countries taking part in the study (Guinea, Libera, Sierra Leone, and Mali).

Inserm is sponsoring the trial in Guinea, where two study centers are operating: one in a rural area and the other in an urban area in Conakry. The trial is being conducted in partnership with the Alliance for International Medical Action (ALIMA) non-governmental organization. The NIH are sponsoring the trial in Liberia and in Mali with three centers overall, and the LSHTM is the sponsor in Sierra Leone with one center. Two centers are responsible for the methodological and operational coordination of the trial: the Euclid/F-CRIN academic platform in Bordeaux, France, and the University of Minnesota in the U.S.

Three pharmaceutical companies are supplying the vaccines tested: Janssen Vaccines & Prevention, B.V., one of Johnson & Johnson’s Janssen Pharmaceutical companies, Bavarian Nordic, and Merck Sharp & Dohme, Corp (MSD outside the U.S. and Canada).

Highly Active Recruitment

Just one year after the project was launched in March 2017, the investigators have already recruited more than 2,000 people in Guinea and Liberia, nearly half of whom are children between the ages of one and seventeen. A new inclusion phase is currently being opened in the centers in the four participating countries, with the objective of including 2,800 more people: half adults and half children. This is important because, in the most recent epidemic, about 20% of Ebola virus cases were in children. Vaccines must be evaluated in this population, particularly in young children between the ages of one and five, whose immune systems are still developing. The inclusion phase should continue into October 2018.

This project required the involvement of an Inserm team made up of doctors, pharmacists, and biologists to prepare and conduct the study. They have been taking turns working in Guinea for the past two years. Our social anthropologists have also undertaken major work in social mobilization and community commitment. They are working with community counselors to explain the value of this project to the local communities and get them on board. The Guineans were traumatized by the epidemic that just ended, and were potentially reluctant to receive vaccine injections, which is an example of why this presence is important and has led to excellent recruitment and monitoring levels for participants,” explains Dr. Eric D’Ortenzio, the PREVAC scientific coordinator for Guinea.

A volunteer is given an inoculation at Redemption Hospital in Monrovia on the opening day in Liberia of the PREVAC trial, a Phase 2 trial of the Ebola vaccine in West Africa
A volunteer is given an inoculation at Redemption Hospital in Monrovia on the opening day in Liberia of the PREVAC trial, a Phase 2 trial of the Ebola vaccine in West Africa. Credit: NIAID

The three immunization strategies being tested are as follows:

  • An initial vaccine of Ad26.ZEBOV followed by a second injection eight weeks later with MVA-BN-Filo, a different vaccine.
  • A single dose of the rVSV ∆G-ZEBOV-GP vaccine with no booster.
  • Two doses of rVSV ∆G-ZEBOV-GP spaced eight weeks apart.

They are compared with placebos administered according to the same injection schedules.

Volunteers must be healthy and children must be at least one year old. They receive either a vaccine or a placebo and are monitored for at least one year, five years if possible. Blood is drawn at different points during the monitoring process to measure the immune response over time, which is the primary objective of the study.

The first results should be available in 2020. They will help us to understand the immune response induced by the various vaccines in adults and children and will make up the scientific basis for possible vaccine approval.