Ebola vaccine trials

The WHO recently admitted it’s failures in responding to the Ebola epidemic. The report highlighted lessons learned and how the WHO plans to make changes to be more responsive to the next big outbreak in the future. The report isn’t exactly the most interesting reading out there as most of it is what you would expect to read, since we already know how the WHO failed in this instance.

But as this Ebola epidemic progresses we are nearing the end of transmission in many areas of the three affected West African countries, Guinea, Liberia and Sierra Leone. As this epidemic expanded beyond what many people initially thought possible, talk started about why there’s no Ebola vaccine. The good news is that researchers have started clinical trials over the past few months, testing various Ebola vaccines against at least one strain of the disease (there are four human disease causing strains, Zaire is normally the most deadly strain and the strain that caused this epidemic).

The WHO, in conjunction with the Health Ministry of Guinea, Medecins Sans Frontieres (MSF), Epicenter, and The Norwegian Institute of Public Health, launched Phase 3 trials of a potential Ebola vaccine in Guinea in early March. These trials are testing the VSV-EBOV vaccine developed by the Public Health Agency of Canada, with plans to test a second vaccine as supplies become available. Researchers are using the “ring vaccination” method to test the vaccine. This method is what helped eradicate smallpox and it entails vaccinating the contacts of a case immediately, with a short delay before vaccinating those further removed from the contact. This way everyone gets vaccinated by the end of the study and there is no placebo vaccination involved.

The National Institutes of Health (NIH) has started a trial with both the VSV-EBOV vaccine (licensed to Merck for further testing) and a vaccine co-developed by the National Institutes of Allergy and Infectious Disease (NIAID) and GlaxoSmithKline, named cAd3-EBOZ, in Phase 2/3 clinical trials in Liberia earlier this year. The clinical trials are being performed under the name PREVAIL which stands for Partnership for Research on Ebola Vaccines in Liberia. However, Liberia has been making great strides at reducing the number of Ebola cases found in the country so there are rumblings that part of the trial will move to Guinea to ensure there are enough people to participate in the study. PREVAIL is using a randomized, double-blinded study design where some people will get the experimental Ebola vaccine (either one vaccine or the other) and some people will get a placebo. This trial is anticipated to be finalized in the summer of 2016.

The CDC is sponsoring a clinical trial with the Sierra Leone College of Medicine and Allied Health Sciences and the Sierra Leone Ministry of Health and Sanitation. This project is called STRIVE (Sierra Leone Trial to Introduce a Vaccine against Ebola). This trial is a Phase 2/3 trial in Sierra Leone, testing the rVSV-ZEBOV vaccine. The trial design is using an unblinded, individually randomized trial where one group will be vaccinated right away and the second group will be vaccinated about 6 months later. There is no placebo vaccine being used in this trial, so everyone enrolled gets vaccinated eventually (similar to the WHO trial).

Novavax started Phase I clinical trials on an Ebola vaccine back in February, in a race to be the first to develop a proven Ebola vaccine. They are performing the Phase I trials in Austrailia with the vaccine they’re calling Ebola GP.

Johnson & Johnson also have a vaccine in Phase I clinical trials being held in England, at Oxford specifically. They are hoping to be in Phase 2/3 trials very soon, once enough data has been gathered from the Phase I trials to move forward.

Other Ebola vaccines may be on their way to trials in the near future, we may also have an approved Ebola vaccine in about a year if the clinical trials go as researchers hope. While the vaccines may be too late to really impact the current Ebola epidemic in West Africa, hopefully they will be distributed widely enough (once approved) to prevent another major outbreak of Ebola. However, it is worth mentioning that vaccine development is only prioritized when there’s a substantial need, so after a disease has already impacted a lot of people. The Ebola vaccine will help against future Ebola outbreaks, but it won’t help against the next unknown or mostly unknown pathogen that causes another major outbreak. That’s where health systems strengthening comes into play. We can’t always predict the next big outbreak and make a vaccine to prevent it, but we can focus on strengthening the healthcare systems found around the world so they are better equipped to deal with that next outbreak, when it comes.

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