A vaccine against Ebola: Searching for a solution to halt the virus

© Shutterstock
© Shutterstock

The Ebola virus was discovered in 1976 by Peter Piot, when a nun fell sick in Zaire and a pilot sent a sample of her blood to the researcher’s lab. The scientists suspected it was yellow fever but, in fact, the cause of the disease turned out to be a threadlike lethal virus, which was given the name « Ebola ». Since the virus infections were confined to only some regions in Africa and the outbreaks where short, nobody thought Ebola would cross the borders the way it is doing nowadays. In December 2013 the first reported case of the outbreak was reported in Guinea. From then on, the virus is spreading at a vertiginous speed in the African continent. The most affected regions are Sierra Leona, Liberia and Guinea. Additionally, Some Ebola cases have been reported in developed countries such as the US, Germany or France.


Players of the vaccine search


In this scenario, in order to prevent future infections and put the epidemic under control, several pharmaceutical companies are putting great efforts on developing a vaccine against Ebola. The pacesetter in this race is ChAd3-ZEBOV vaccine. This vaccine is being produced by the US National Institute of Allergy and Infectious Diseases (NIAID) and Okairos (a part of GlaxoSmithKline). Phase I trials started in the UK and the US in September and in Switzerland and Mali in October. Satisfactory results were revealed for the trial in the US. Concerning the rest of them, the outcomes will be known by the end of the first quarter of 2015.

The rVSV vaccine is being developed by New Link Genetics and Merck Vaccines USA, along with the Public Agency of Canada. Phase I trials started in the US in October. They were also accomplished in Gabon, Germany, and Switzerland in November as well as in Canada and Kenya In December.

Johnson&Johnson’s, along with Bavarian Nordic, have also committed to the fight against Ebola. In fact, the companies have destined $200 million to the development of a vaccine, which, unlike ChAd3, will require a two-step administration. In other words, the first shot will serve to prime the immune system and the second one will boost it. Janssen contemplates to produce more than one million doses of vaccine in 2015, from which 250.000 are expected to undergo clinical trials by May 2015. In January 2015, Johnson&Johnson unveiled the start of the first PI clinical trial, which is being carried out in the UK.

Novavax, a biotech company centered on recombinant nanoparticle vaccines and adjuvants, has developed the Ebola GP vaccine, which is a recombinant nanoparticle glycoprotein coming from the Ebola virus adjuvanted with Matrix-M. Novavax has recently started the Phase I clinical trials in Australia.

The Russian Federal Ministry of Health is also developing a recombinant influenza candidate Ebola vaccine, that will begin Phase I trials by the second half of this year.


It is easy to develop a vaccine against Ebola?


While the development of these vaccines could help us keep Ebola under control, it exists challenges and concerns that should be assessed, ranging from technical issues to unpredictability of the virus. As it propagates, it mutates and the virus could get either more or less virulent. In the second case, people would stay alive for longer and the chances for the virus to infect other individuals would increase. Also, if the virus continues to mutate as fast as the actual rate, the vaccines, which are being developed could lose efficacy or they could even become ineffective.

Moreover, Ebola has the ability to change its shape thanks to the VP40 protein, depending on the function it wants to perform. The different shapes that the Ebola can adopt have implications for drug design. The therapies should target all the forms in order to neutralize the virus.

The technical and logistical issues that need to be addressed before performing the clinical trials should not be overlooked either. For example, vaccines should be stored at a temperature of -80°C, which can be a problem taking into account that the electricity in some communities is not reliable. One solution could be the lyophilization of the vaccine. In this case, it could be stored in regular freezers.

Another impediment that needs to be overcome is speeding up the quality approval process required by regulators for vaccines. This could be accomplished by running several quality controls in parallel.

An issue that is being addressed is the allocation of vaccines. Who will be vaccinated first? Will be enough doses available for all the people? The number of doses required as well as the availability will depend on the results of the clinical trials and the decisions that will be made by ministries of health.