The alacrity and eagerness shown by the research community to find a safe and efficacious vaccine against the deadly Ebola virus has borne fruit. The interim results of a Phase III clinical trial in Guinea using a novel virus vaccine (rVSV-ZEBOV) have shown 100 per cent efficacy after 10 days of vaccination. People who received it three weeks after randomisation (delayed vaccination) served as the control group. Since the estimated efficacy is based on results from a small group of volunteers comprising 2,014 people who were vaccinated immediately after randomisation, the actual efficacy level will be known only when it is tested on a larger population. According to the World Health Organization, which sponsored and led the trial, the efficacy will be between 75 and 100 per cent. Given the promise, the trial is set to continue with everyone who has come in direct contact with an infected person (index case) and those exposed to the primary contacts set to receive the vaccine immediately. As of July 26, there have been 3,786 cases and 2,520 deaths in Guinea since the first outbreak more than a year ago; according to the WHO, as of July 26 there have been 27,748 cases and 11,279 deaths from Ebola in the West African countries of Guinea, Liberia and Sierra Leone.
The virus is transmitted through direct contact with the body fluids of a sick person or a cadaver. Given the falling incidence, the Ebola c¸a Suffit (“Ebola this is Enough”) trial used a novel “ring” vaccination design, that was earlier used for smallpox eradication in the 1970s; people at high risk of infection owing to direct contact with an index patient or who had been exposed to the primary contacts, were chosen. Considering that people were suspicious of health-care workers during the initial stages of the outbreak, the active participation of families and communities in identifying those at risk for the trial is a testimony to the commitment to win the war against the virus. In addition to the protection that is extended to those who have been vaccinated, the trial has confirmed that the ring vaccination strategy will “most likely” be effective at the population level by creating herd immunity. Thus the vaccine can “hopefully stop” disease transmission in Guinea once it is administered to all the contacts. Similar results can be expected when the vaccine is used in Liberia and Sierra Leone. This is a big victory and a much needed weapon to fight the virus that killed many, devastated economies and caused the health-care systems to collapse in the three countries. The vigil should now continue, and it should be ensured that Ebola never makes a comeback anywhere on earth.
