Ebola Vaccine Will Do Little for Current Crisis
The National Institute of Allergy and Infectious Diseases (NIAID), the branch of the NIH that oversees investigations into infections ranging from Ebola to AIDS to Lyme, announced today that the first of a series of vaccine trials aimed at preventing acquisition of Ebola will be launched next week.
The first trial will be conducted in 20 healthy, uninfected volunteers at the NIH in Bethesda, Maryland. They will be enrolled into the trial three people at a time with frequent monitoring of the vaccine safety. Later this year, a related vaccine will be studied, again in a small number of healthy uninfected volunteers, in Great Britain and in the African countries of Mali and Gambia, which are unaffected by Ebola but which have strong healthcare infrastructures. Very preliminary talks also have commenced to conduct a trial in Nigeria, which has seen more than a dozen Ebola cases during the current outbreak.
The news is surely encouraging, coming as it does on the heels of the news from WHO, which now is preparing for an epidemic of up to 20,000 people, including the 3,000-plus infected thus far, with 1,552 deaths.
Yet NIAID director Dr. Anthony Fauci was very careful to state that for the current outbreak in West Africa, the best approach will not be the vaccine or any new treatments, but rather the approach being used today and last week and last month and last year: early diagnosis, prompt isolation, and use of “personal protective equipment” including gowns, gloves, and masks.
In other words, the vaccine being studied almost certainly will have no impact on the current West Africa crisis. Given the pace of useable science, even with the compressed, hurry-up-already system the candidate vaccine is being ushered through, preliminary results on safety and the vaccine’s ability to provoke a meaningful immune response will not be available until the end of the calendar year—at a point when the now 6-month long epidemic likely will have finally fizzled out.
The science behind the vaccine is extremely interesting and exploits all the latest in vaccinology. A critical gene from the Ebola virus is clipped out, rendering the Ebola virus no longer capable of replication; the Ebola gene is then placed into a different living virus—in this case a chimpanzee virus called adenovirus type 3. The chimp adenovirus is used for a couple of reasons. First, the human recipients of the vaccine will not have pre-existing immunity to it. Ironically, a problem in the world of what is called “vector vaccines” like the chimp-adeno-Ebola vaccine occurs when the recipient already has immunity to the vector virus—adenovirus in this circumstance. If immunity already exists, the recipient will destroy the vaccine product before the vaccine product can trick the exact same immune system into generating fresh immunity to the spliced gene—in this circumstance, the Ebola gene. Use of a non-human vector hopefully circumvents this.
In addition, it is hoped that non-human adenovirus will be safer than adenovirus. Almost two decades ago, at the dawn of viral vector and gene therapy, a young man with a congenital disease died from overwhelming inflammation provoked by adenovirus infusion and infection. The adenovirus he received was simply a vector, bringing a missing gene to his cell. His death cast a pall over the field that remains today; it also makes each investigator and volunteer particularly keen to assure study safety.
The vaccine being studied will contain two genes, one each from two distinct strains of Ebola: the “Zaire” strain that is causing the current epidemic, and the “Sudan” strain. Other trials, to begin in the fall, will study a monovalent vaccine that has a gene only from the Zaire strain.
This work builds on years of previous Ebola vaccine trials conducted by the NIH. None of the specific products have moved forward, but each has revealed new information regarding how best to build a safe and effective vaccine.
Stacked against the ongoing human tragedy playing out in West Africa, the methodical pace of science can seem callous if not intentionally cruel. Yet this is the way of all investigation, an untidy world of trial and error, accident and earned insight, high drama and limited yield. Though all are clamoring for a futuristic solution to Ebola, control in 2014 will depend, as Dr. Fauci made clear, on reliable execution of the most basic and unglamorous approaches to outbreak management: people carefully and caringly treating those with the disease.