To date, at least 15 vaccines are being developed (in North America, Europe, Russia and China), with four main candidates in varying advanced stages of human testing. These include the two most advanced – VSB-EBOV and ChAd3-ZEBOV – as well as a prime-boost regimen of Ad26- and MVA-EBOV developed by Johnson & Johnson and a recombinant particle made of EBOV glycoprotein produced in an insect cell line, developed by the biotech company Novavax.
The two lead vaccine candidates started human clinical trials in September 2014 and data on their safety and immunogenicity profiles were ready by December-January, breaking all records in terms of vaccine trial Phase I timelines. WHO played a key role in this endeavour, by identifying and coordinating numerous trial sponsors to test the vaccines contemporaneously in the US, Canada, and several countries in Europe and Africa.
These two vaccines are now in Phase II/III trials in the three affected countries. The trial collaborations underway are: a ring vaccination trial of VSV-EBOV in Guinea, organized through a large international consortium including WHO, MSF, Canada, Norway and universities in the UK, Switzerland and the US; and a cluster based, non-blinded, individually randomized trial of VSV-EBOV in Sierra Leone under a Sierra Leonean-US-CDC collaboration. A Phase II trial of both vaccines was carried out in Liberia under a Liberian government – US-NIH collaboration. This trial was completed at the end of April, and it is not known if trials in Liberia will continue. In the meantime, phase II trials of the GSK vaccine are slated to start in Cameroon, Ghana, Mali, Nigeria and Senegal in the the second half of 2015.
Pharmaceutical companies developing the vaccines have committed to ramp up production capacity in case of proven vaccine efficacy and the need for deployment. This could be the fastest vaccine roll-out in history.