Vaccine Stops Ebola in its Tracks

Ebola (Zaire ebolavirus) is one of the deadliest diseases known to mankind. After entering the body, it wreaks havoc on the immune system by causing cells to explode, leading to internal bleeding and the destruction of nearly every single organ in the body. The Ebola virus contains a type of genetic material called RNA, which contains the blueprint for assembling new virus particles. In order to create new viruses, the virus must infiltrate a living cell, where it hijacks the host cell’s machinery to make copies of itself. Often, this appropriation of the cell’s replication machinery comes at the expense of the cell being unable to make all of its own needed machinery, leading to an inability to function properly and even death of the cell. After the new virus is fully assembled, the virus “buds” from the cell, using the cell’s own outer coat to make a capsule for traveling to new cells and restarting the cycle. Scientists have found that Ebola specifically targets liver cells, immune system cells, and endothelial cells, which line the inside of blood vessels. By targeting liver cells, the body’s ability to clear toxins out of the bloodstream is compromised, and by infecting the immune system, whose cells travel everywhere in the body, Ebola has an opportunity to rapidly increase its area of infection. Ultimately, organ failure and shock caused by internal bleeding lead to death.

The virus earned its reputation with an alarming fatality rate of over 90 percent. According to the Center for Disease Control, the virus spreads to people via direct contact with blood, body fluids, and animal tissues. This is especially problematic in countries like the Democratic Republic of Congo and Guinea, where living conditions are unsanitary and clean medical equipment is sparse. Ebola was so detrimental to large populations, primarily those in western Africa, partly because there were no methods of reducing the incidence of cases, or new people who had contracted the disease.

But not anymore.

The U.S. Food and Drug Administration (FDA) authorized the first Ebola vaccine, sold under the brand name Ervebo, in mid-December of 2019. The new vaccine contains a virus genetically engineered to provoke a neutralizing immune response against the Ebola virus. This vaccine works similarly to those for other highly infectious diseases, such as polio. However, instead of exposing the recipient to actual Ebola microbes, scientists altered the genetic material in a related virus to stimulate similar effects. The reason for not exposing the person directly to the virus is because the speed with which the virus attacks the immune system overpowers the body too quickly for a sufficient response to take place. Instead, the recipient is exposed to these weakened viral microbes, and in turn, produces antibodies that bind to the virus’s antigens, as well as memory cells for future immunity.

Scientists began researching a treatment for Ebola after outbreaks in the Democratic Republic of Congo triggered a world-wide scare in early 2010. The vaccine was tested during the 2014-2016 outbreak in West Africa and was designed to protect individuals older than 18 from infection. “I’m excited that we are there. And of course, it has taken too long,” said Dr. Heinz Feldmann, the designer of Ervebo, in an interview with The New York Times in December 2019. Dr. Feldmann explained that the vaccine could prove to be a crucial tool in containing the outbreaks now that it is being used in a real-world setting.

However, a critical issue that arose during the experimental trials of Ervebo was how to prevent transmission of a virus that was already so widespread. As Ebola was already so extensive within Africa, scientists and researchers found it difficult to accurately predict the effects of the vaccine. So, they used the “ring-vaccination” method, in which people already infected were vaccinated in an attempt to build a wall of immunity that cut off viral transmission. Following a large-scale ring-vaccination plan carried out during the Democratic Republic of Congo outbreak, the World Health Organization published the preliminary results of its research in April 2019: Ervebo had been 97.5 percent effective at stopping Ebola transmission.

“The belief was that the virus was so aggressive that you couldn’t find a vaccine that would protect people,” Dr. Feldmann explained. But now, with Ervebo on the FDA’s official list of approved substances, there has been a paradigm shift in the way the world views Ebola outbreaks. During a later outbreak in the Democratic Republic of Congo during the summer of 2019, the vaccine was used, and what was once 1,706 infected individuals was rapidly reduced to zero.

While cases of Ebola in the United States are extremely rare, the FDA considers the vaccine a crucial tool in stopping the spread of the disease, and it was approved for medical use in the U.S. on December 20, 2019. Since then, 250,000 people have been vaccinated. Merck also received permission from the European Commission to market Ervebo in October of 2019.

“Ebola virus disease is [a] rare but severe and often deadly disease that knows no borders. Vaccination is essential to help prevent outbreaks and to stop the Ebola virus from spreading when outbreaks do occur,” said Dr. Peter Marks, M.D., Ph.D., director of the FDA’s Center for Biologics Evaluation and Research. Not only is the FDA’s approval of Ervebo a major advancement in protecting against Ebola, but it is also crucial in advancing the U.S. government’s preparedness efforts.

Though the FDA’s official press release about the vaccine does not specify who Ervebo will be available to, there have been some concerns regarding the age restriction of 18 and older for the vaccine. A study done on the effectiveness of Ervebo administered a dose of Ervebo to 234 children and adolescents six to 17 years of age across three trials. In a Phase One trial observing children six to 17 years of age, results at Day 28 and Day 180 post-vaccination were similar to those observed in adults in the same study. In other words, the vaccine is as effective in children as when it is used on adults. However, the reasons for the European Medicines Agency’s (EMA) decision to withhold the vaccine from children are still uncertain. More Ervebo studies are yet to be completed, but the EMA has transferred the responsibility of submitting the results to pediatricians specializing in Ebola prevention.

Though we have yet to definitively uncover its effects on children, the discovery of the Ebola vaccine, Ervebo, and its approval by the FDA have solidified a monumental breakthrough in the ongoing fight against infectious diseases. Developing the vaccine for a seemingly unpreventable disease has given scientists hope for other deadly infections. The development of Ervebo has also shone a light on the effectiveness of genetic engineering in producing a viable vaccine. The idea of using a virus to fight another virus, similar to the phrase “fighting fire with fire,” has introduced a new and efficient method for the future of medicine.