Vaccine for Ebola Reaching Last Trial Phase


The Ebola epidemic seems to be on the decline, with the last infected patient being recently released in Liberia. However, the World Health Organization (WHO) warns that the dangers of the epidemic are not completely gone, with numerous new cases being reported in the two most affected countries of the world, Guinea and Sierra Leone. In this situation, a race to develop a working vaccine for Ebola is at full speed with the possibility of a last trial phase, and promising candidates are being fast-tracked through the bureaucratic channels, under the careful supervision of WHO, in order to find the best preventative solution.

A vaccine works by injecting a small dose of a weak virus strain into a healthy individual, to create an immune response where virus-specific antibodies are being produced, which will then prevent a future infection. From several candidates for the Ebola vaccine, two developers have risen as the most promising, and are now ready for the final testing phase. The vaccine created by the Canadian Public Health Agency, in collaboration with NewLink Genetics and Merck Vaccines from the US, is set to start it’s Phase III trials on March 7th , with GSK’s version soon to follow.

For these two, the results from the initial trials, that took place in countries like the UK, USA and Switzerland, were deemed satisfactory by the evaluating boards and green-light was given for further testing. The first human trial of the Canadian vaccine showed an active immune response, but there was not enough data to predict if the vaccine would work in a potential infectious situation. From here stems the need for a final phase of testing, which will take place in the most affected parts of Guinea and it is expected to last for 60 days, followed by another 84 day period of observation, and will be conducted with the support of Médecins sans Frontières. First to receive the vaccine will be the medical personnel that work directly with the patients, together with part of the population.

The method chosen for Phase III is the ring design, that works by identifying the latest reported illness and inoculating the subject’s closest contacts. They will receive the vaccine upon consent, in a two-step fashion. The first half right away, while the other will be injected after a delay of three weeks. This was decided in order to have a control group for comparison, while, at the same time, aiming to vaccinate the entire group of contacts by the end of the trial period, and form a protective ring around the infected patient.

Another company that joined the works is Johnson & Johnson, in collaboration with Bavarian Nordic, which developed a vaccine to be administered in two separate doses. Their trials began in January 2015, intending to provide another option for the containment of the epidemic.

After the trials end, the Global Vaccine Alliance will provide the funds for the first doses. There will be around several million jabs of the vaccine, that will prove to be the most effective. It is expected that by late 2015, a safe vaccine will be available to the population.

While a preventative method is being researched at a fast pace, treatment options for the people already diagnosed with Ebola are slower to develop. The most promising seemed to be Favipiravin, created in Japan, that became the best option for the early stages of the infection, and Brincidofovir, which had already begun testing in Liberia, but its trial came to a halt when no more cases were reported in the country. Besides these drugs, the blood transfusion therapy is seen as very effective, with as much as seven out of eight survivors reported from the latest 1995 Ebola epidemic in Congo. It requires blood taken from a recovered patient, from which antibodies are selected and introduced into an infected person’s bloodstream, to then fight the disease.

Although the trials face many obstacles, like the cooperation of the population and proper conditions to store the vaccines, a positive result would mean adding another prevention tool to the medical field by creating the first Ebola vaccine in history. Time will tell if the Ebola vaccine will be ready once it completes the last trial phase.

By Rut Andrada Baston

World Health Organization (1)
World Health Organization (2)
BBC News

Photo by wader – Flickr License

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