Final trial shows Ebola vaccine “highly protective”, says WHO

The World Health Organisation says an experimental Ebola vaccine has proved "highly protective" against the virus in a major trial in Guinea. According to results published in the journal Lancet, the experimental vaccine is the first to prevent infection from "one of the most lethal known pathogens." The findings add weight to early trial results […]

The World Health Organisation says an experimental Ebola vaccine has proved "highly protective" against the virus in a major trial in Guinea.

According to results published in the journal Lancet, the experimental vaccine is the first to prevent infection from "one of the most lethal known pathogens."

The findings add weight to early trial results published in August 2015.

The vaccine rVSV-ZEBOV was trialled in a study involving 11,841 people in Guinea last year.

Some 5837 people received the vaccine, and no Ebola cases were recorded 10 days or more after vaccination.

In comparison, there were 23 cases 10 days or more after vaccination among those who did not receive the vaccine, said WHO, which led the study together with Guinea’s health ministry, Medecins sans Frontieres and the Norwegian Institute of Public Health.

"While these compelling results come too late for those who lost their lives during West Africa’s Ebola epidemic, they show that when the next Ebola outbreak hits, we will not be defenceless," said Dr Marie-Paule Kieny, WHO’s Assistant Director-General for Health Systems and Innovation, and the study’s lead author.

rVSV-ZEBOV’s maker Merck, Sharpe & Dohme, has received top designations from the US and European regulatory agencies, enabling the vaccine to get faster review by regulators when it is submitted.

Sporadic outbreaks of Ebola have hit mostly eastern Africa but the latest which killed 11,300 people and crippled health systems in West Africa, forced need for a vaccine.

Trial and tests

Guinea’s coastal region of Basse-Guinée was still seeing new Ebola cases in 2015 when the trial started and was chosen as site of trial.

Researchers used a ring approach, the same method used to eradicate small pox, vaccinating everyone in contact with an infected person in the preceding three weeks.

They included people who lived in the same household, were visited by the patient, or were in close contact with the patient, their clothes or linen, as well as certain "contacts of contacts", researchers reported.

A total of 117 clusters (or "rings") were identified, each made up of an average of 80 people.

In initial trial, the vaccine was given immediately or after a three-week delay for adults over 18.

After interim results were published showing the vaccine’s efficacy, all rings were offered the vaccine immediately and the trial was also opened to children older than 6 years, according to researchers.

The result shows high efficacy among those vaccinated; it also showed unvaccinated people in the rings were "indirectly protected" through herd immunity.

More research is need to measure the effect of herd immunity with regards to Ebola vaccine.

"Ebola left a devastating legacy in our country. We are proud that we have been able to contribute to developing a vaccine that will prevent other nations from enduring what we endured," said Dr KeÏta Sakoba, Coordinator of the Ebola Response and Director of the National Agency for Health Security in Guinea.

To assess safety, people who received the vaccine were observed for 30 minutes after vaccination, and at repeated home visits up to 12 weeks later, according to a release by WHO.

Approximately half reported mild symptoms soon after vaccination, including headache, fatigue and muscle pain but recovered within days without long-term effects.

Effects

Researchers noted one patient developed a fever, another developed allergic reactions and a third had flu-like illness, but all three recovered without long term effects.

Further studies hope to get biologic samples from people who have taken the vaccine to analyse immune response.

One is ongoing alongside the vaccine trial among front line health workers in Guinea.

"This both historical and innovative trial was made possible thanks to exemplary international collaboration and coordination, the contribution of many experts worldwide, and strong local involvement," said Dr John-Arne Røttingen, specialist director at the Norwegian Institute of Public Health, and the chairman of the study steering group.

Ready market

GAVI, the Vaccine Alliance, in January provided $5 million to Merck to buy the vaccine once it is approved, prequalified and recommended by WHO.

According to that agreement, Merck will ensure 300,000 doses of the vaccine are available for emergency use in the interim and will submit it for licensing by the end of 2017.

WHO can also list the vaccine for, like other experimental, vaccines, medicines and testing, for use prior to formal licensing.