Ebola Vaccine: Is It Safe?

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Currently, there is no FDA-approved Ebola vaccine available to individuals; consequently, there is no Ebola vaccine that the FDA or the CDC considers "safe" as of September 2014. However, there is a lot of activity going on related to the development of a safe and effective Ebola vaccine. Consequently, the answer about an available, safe anti-Ebola vaccine may change in the near future.

For background information, readers should know that the Ebola virus is very infectious and is transmitted easily from person to person; it is a deadly viral infection that may kill 60%-90% of humans that it infects. Ebola virus infections damage blood vessels and can cause internal bleeding, shock, and eventually death. Until recently, Ebola viral infections were contained by isolating those few people infected in small settlements in several African countries. However, in 2014, a large outbreak of Ebola infections occurred in several East African countries (Liberia, Nigeria, Sierra Leone, and Guinea) and, to date, over 1,900 people have died from this infection. This is the largest Ebola outbreak ever recorded. Since there is no safe or effective vaccine and no readily available drugs that are effective in treating the disease, there is concern that this outbreak will continue and spread into many other countries.

Prevention of Ebola viruses from infecting humans is the best way to protect individuals. In general, this is done by isolating individuals who can transmit the viruses and/or by vaccinating uninfected individuals with a safe and effective vaccine. Isolating individuals who are infected is the current method used to protect uninfected people from Ebola viruses, but unfortunately, in this current outbreak, isolation techniques have not been very effective. Vaccine development began in 2003 against Ebola viruses but none currently are available. However, because of this Ebola virus outbreak, the NIH (National Institutes of Health) announced that initial treatment testing of an investigational vaccine to prevent Ebola virus disease will begin in September 2014. This phase 1 clinical trial will help investigators at the NIH and GlaxoSmithKline (GSK) determine the safety and efficacy of a new vaccine against Ebola. Another major trial of a vaccine will occur this fall; this vaccine is being developed by the Public Health Agency of Canada and NewLink Genetics Corp. In addition, the NIH has partnered with the British consortium to test the National Institutes of Allergy and Infectious Diseases/GSK vaccine in the United Kingdom and in the West African countries of Gambia and Mali. Finally, NIH is supporting two other experimental vaccine producers (Crucell and Profectus Biosciences) and is collaborating with Thomas Jefferson University to develop a vaccine based on the established rabies vaccine. NIH hopes that one or more of these experimental vaccines may be shown to be safe and effective against Ebola virus infections by late 2014 or early in 2015. Most of the companies and even the U.S. government hold patents on each type of anti-Ebola vaccine. Vaccines are designed to stimulate an immune response against Ebola viruses that will protect uninfected individuals who are exposed to live Ebola viruses. The vaccines do not contain live Ebola viruses, only antigens or parts of the virus that can stimulate a protective immune response. The vaccines cannot cause Ebola infections.

Safe and effective anti-Ebola vaccines are designed to protect uninfected individuals; they are not used to treat individuals already infected with Ebola viruses. Antiviral drugs are designed to treat ongoing viral infections. For Ebola infections, all of the antiviral drugs are currently experimental; this includes the ZMapp chimeric antibody that was used on several individuals (two of seven patients treated still died). Other experimental treatment drugs for Ebola-infected people may include the following: TMK-Ebola, AVI-7537, favipiravir, estrogen receptor modulators, BCX-4430, and ST-383. These drugs are designed to disrupt Ebola virus replication and/or to neutralize the virus pathogenic mechanisms. None are currently available commercially for human use.

The current Ebola outbreak illustrates how easily a virus can escape isolation techniques and shows that in the days of unimpeded movement of people via cars, buses, trains, and planes, even a disease like Ebola virus infection that was once thought of as a rare but potentially fatal disease can suddenly begin epidemics that we are poorly equipped to stop. Early development and stockpiling of safe and effective vaccines and/or techniques to produce such vaccines quickly should be a worldwide priority.

REFERENCES:

United States. Centers for Disease Control and Prevention. "Questions and Answers on Experimental Treatments and Vaccines for Ebola." Aug. 29, 2014. <http://www.cdc.gov/vhf/ebola/outbreaks/guinea/qa-experimental-treatments.html>.

United States. Federal Register. "Prospective Grant of Exclusive License: Multivalent Vaccines for Rabies Virus and Ebola and Marburg (Filoviruses)." Mar. 31, 2014. <https://www.federalregister.gov/articles/2014/03/31/2014-07023/prospective-grant-of-exclusive-license-multivalent-vaccines-for-rabies-virus-and-ebola-and-marburg>.


Last Editorial Review: 9/8/2014