A vaccine against the deadly Ebola virus has led to 100% protection and could transform the way Ebola is tackled, preliminary results suggest.
There were no proven drugs or vaccines against the virus at the start of the largest outbreak of Ebola in history, which began in Guinea in December 2013.
The World Health Organization (WHO) said the findings, being published in the Lancet, could be a “game-changer”.
Experts said the results were “remarkable”.
This trial centred on the VSV-EBOV vaccine, which was started by the Public Health Agency of Canada and then developed by the pharmaceutical company Merck.
It combined a fragment of the Ebola virus with another safer virus in order to train the immune system to beat Ebola.
A unique clinical trial took place in Guinea. When a patient was discovered, their friends, neighbours and family were vaccinated to create a “protective ring” of immunity.
This could be the breakthrough the world has been waiting for.
There is caution as the results are still preliminary, with more data coming in.
But officials at the WHO believe the effectiveness of the vaccine will end up being between 75% and 100%.
If such a vaccine was available 18 months ago then thousands of lives could have been saved.
There are still other vaccines being trialled – notably from GSK and Johnson&Johnson – although as the number of cases continues to fall it is becoming increasingly difficult to prove how effective they are.
Ebola will inevitably come again.
The hope now is that the legacy of this unprecedented outbreak will be a vaccine that means a tragedy of this scale can never be repeated.
One hundred patients were identified in the trial between April and July and then close contacts were either vaccinated immediately, or three weeks later.
In the 2,014 close contacts who were vaccinated immediately there were no subsequent cases of Ebola.
In those vaccinated later there were 16 cases, according to the results published in the Lancet medical journal.
The WHO says it is so far 100% effective, although that figure may change as more data is collected.
Close contacts of Ebola patients in Guinea will now be vaccinated immediately. And since the vaccine has been shown to be safe, that process will also be extended to include children.