Ebola Zaire vaccine (live, attenuated)

Identification

Summary

Ebola Zaire vaccine (live, attenuated) is a vaccine used in the prophylaxis of Ebola virus disease caused by the species of Zaire ebolaviruses.

Brand Names

Zabdeno

Generic Name

Ebola Zaire vaccine (live, attenuated)

DrugBank Accession Number

DB15595

Background

Ebola virus vaccine is a vaccine used to prevent Ebola virus disease caused by Zaire ebolavirus in adults, prevent outbreaks, and reduce the extent of the virus spreading in case of outbreaks.⁶ Ebola virus disease, formerly known as Ebola hemorrhagic fever, is a rare but severe and often deadly disease. It is highly contagious: human to human transmission occurs from contact with body fluids from infected patients.⁴ It is characterized by fever, headache, myalgia, and gastrointestinal symptoms. These may be accompanied by hypotension and respiratory, kidney and liver failure, as well as internal and external bleeding.^1,2 In the Filoviridae family, there are five unique Ebolavirus species that are each named after the geographical region where it was first identified. The mortality rate of the Zaire species is about 80%.²

Confirmed outbreaks of Ebola virus disease have been documented since the 1970s, mostly in Sub-Saharan Africa, where Ebola first appeared in 1976 near the Ebola River in Zaire (presently referred to as the Democratic Republic of the Congo) and Sudan.¹ Between 2014 and 2016, Ebola outbreaks occurred in West Africa, leading to more than 11,310 total deaths during this time in Guinea, Liberia, and Sierra Leone.² In 2016, this epidemic was exhausted after these countries were declared Ebola-free by 2016, and the World Health Organization (WHO) lifted the Public Health Emergency of International Concern (PHEIC) status on the West Africa Ebola outbreak.⁹

The first live, attenuated Ebola virus vaccine was developed by a team of Canadian researchers at Canada’s National Microbiology Laboratory and was later patented by the Canadian government.⁸ In non-human primate clinical trials, the vaccine was effective in inducing an immune response against the Ebola viruses.³ This vaccine was later sold to NewLink Genetics, a biotech company that held the license to the vaccine from 2010 to 2014, although the vaccine was not marketed.⁸ In 2014, Merck Inc. signed a licensing agreement with NewLink for further development and marketing. Ervebo, the marketed Ebola virus vaccine by Merck, was first approved by the European Commission in November 2019 after the European Medicines Agency recommended it be licensed. In December 2019, Ervebo was approved by the FDA in the United States. Ervebo consists of an envelope glycoprotein of the Zaire ebolavirus (Kikwit 1995 strain) fused into a vesicular stomatitis virus (VSV) backbone.⁶ By introducing the relatively inactive viral protein to the patient, the patient’s immune system learns to recognize and attack the virus if he or she is exposed to it in the future.

Type

Biotech

Groups

Approved

Biologic Classification

Vaccines
Attenuated

Synonyms

Ebola Zaire vaccine (live)
Ebola Zaire Vaccine (rVSV∆G-ZEBOV-GP, live)
Recombinant Vesicular Stomatitis Virus (rVSV) strain Indiana with a deletion of the VSV envelope glycoprotein (G) replaced with the Zaire Ebola Virus (ZEBOV) Kikwit 1995 strain surface glycoprotein (GP)

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Pharmacology

Indication

Ebola Zaire vaccine is indicated for active immunization of individuals 12 months of age or older to protect against Ebola Virus Disease (EVD) caused by Zaire Ebolavirus.^7,10

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Associated Conditions

Indication Type	Indication	Combined Product Details	Approval Level	Age Group	Patient Characteristics	Dose Form
Prophylaxis of	Ebolavirus disease		••••••••••••			••••••••••

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Pharmacodynamics

Ebola Zaire vaccine protects against the Ebola virus infection and disease by introducing a protein produced by the Zaire ebolavirus and initiating the body's normal immune responses against the virus. In clinical trials consisting of subjects receiving the Ebola virus vaccine, the vaccine virus RNA was detected in the plasma samples of most subjects within the first week after intramuscular injection.⁶

Mechanism of action

Ebola virus disease occurs when the virus comes into contact with the host tissue and invades the tissue by breaking in the mucosa or skin. Exposure can occur through animal-to-human or human-to-human transmission from blood and other bodily fluids of the virus-infected animal or human.⁴ The viral genome then replicates inside the cell, causing gene modulation in host cells - including monocytes, macrophages, and dendritic cells - and promote cell apoptosis, releasing the viral particles to extracellular tissue.² The virus can further disseminate the infection by migrating to the regional lymph nodes, liver, and spleen to cause lymphadenopathy, hepatocellular necrosis, and lymphopenia.^2,4 Ebola virus can cause dysregulation of the host immune system by inducing the host expression and release of pro-inflammatory mediators, including interferons, interleukins (IL-2, IL- 6, IL-8, and IL-10), and tumour necrosis factor α (TNF-α).⁴ These inflammatory processes promote endothelial activation and reduced vascular integrity. Furthermore, the release of tissue factors and increased nitric oxide levels lead to disseminated intravascular coagulation (DIC) and hypotension seen in the Ebola virus disease, respectively.^2,4 The incubation period after the Ebola virus infection is 1-21 days.⁴

By introducing the attenuated viral protein to the patient, the Ebola Zaire vaccine elicits strong cellular and antibody responses against the virus. The vaccine produces a long-term immunity and protects the patient from Ebola virus infection and disease when he or she is exposed to Zaire ebolavirus in the future.⁵ However, the relative contributions of innate, humoral and cell-mediated immunity to protection from Zaire ebolavirus is not fully understood.⁶

Absorption