rVSV-ZEBOV

rVSV-ZEBOV
Name	rVSV-ZEBOV
Type	Viral vector vaccine
Target	Zaire ebolavirus
Vaccine for	Ebola virus disease
Trade names	Ervebo
Legal status	* World Health Organization prequalified * FDA approved * EMA approved
CAS number	2410990-95-1
DrugBank	DB15650
UNII	1K0E7IDM7J

rVSV-ZEBOV is a viral vector vaccine designed to protect against infection by Zaire ebolavirus, the causative agent of the most severe form of Ebola virus disease. Developed through a collaboration between public health agencies and the private sector, it is the first vaccine to receive full regulatory approval for the prevention of Ebola. The vaccine's approval by bodies like the Food and Drug Administration and the European Medicines Agency marked a pivotal advancement in global health security, particularly for regions in Sub-Saharan Africa prone to outbreaks.

Development and history

The foundational work for this vaccine began in the early 2000s at the Public Health Agency of Canada's National Microbiology Laboratory in Winnipeg. Key scientists, including Heinz Feldmann and Steven M. Jones, utilized a genetically engineered vesicular stomatitis virus as a vector. Following promising preclinical studies, the intellectual property was licensed to the American biotechnology firm NewLink Genetics. In 2014, during the devastating West African Ebola virus epidemic, the vaccine candidate was urgently advanced through a partnership with the pharmaceutical giant Merck & Co., which assumed further development. Critical support and funding for clinical trials were provided by organizations such as the World Health Organization, the Wellcome Trust, and various national institutes like the National Institute of Allergy and Infectious Diseases.

Mechanism of action

The vaccine is a recombinant, replication-competent construct where the gene for the vesicular stomatitis virus glycoprotein is replaced with the gene encoding the glycoprotein of the Zaire ebolavirus Kikwit strain. This engineered viral vector infects host cells and directs the production of the Ebola glycoprotein, which is presented on the cell surface. This presentation stimulates a robust adaptive immune response, including the production of neutralizing antibodies by B cells and the activation of cytotoxic T cells. The immune system thus generates a memory response against the Ebola glycoprotein, providing protection without exposure to the live, pathogenic Ebola virus.

Clinical trials and efficacy

Pivotal evidence of efficacy came from the "Ebola ça Suffit" ring vaccination trial conducted in 2015 in Guinea by a consortium including the World Health Organization, Médecins Sans Frontières, and the Norwegian Institute of Public Health. The trial, led by researchers like Ana Maria Henao-Restrepo, employed a ring vaccination strategy adapted from the successful campaign against smallpox. Interim results published in The Lancet demonstrated 100% efficacy in immediate contacts. Subsequent trials, such as the PREVAIL study in Liberia supported by the National Institutes of Health, and the Phase 3 trial in Sierra Leone, confirmed high immunogenicity and protective efficacy, leading to its regulatory approvals.

Manufacturing and distribution

Merck & Co. manufactures the vaccine, marketed as Ervebo, in its facilities. The product requires strict cold chain maintenance, stored at between -60°C and -80°C, posing significant logistical challenges for use in resource-limited settings. Distribution during outbreaks is coordinated by international bodies like the World Health Organization and Gavi, the Vaccine Alliance, often in conjunction with ministries of health in affected countries such as the Democratic Republic of the Congo. The establishment of a global stockpile managed by the International Coordinating Group on Vaccine Provision ensures rapid deployment to contain emerging epidemics.

Usage in outbreaks

The vaccine has been deployed extensively under compassionate use and investigational protocols during major outbreaks in the Democratic Republic of the Congo, including the 2018–2020 epidemic in North Kivu and Ituri provinces, and the 2021 outbreak in Guéckédou, Guinea. Its use is central to the ring vaccination strategy, where contacts and contacts of contacts of confirmed cases are immunized to create a protective buffer. These campaigns, often led by the Ministry of Health (Democratic Republic of the Congo) with support from World Health Organization and Médecins Sans Frontières teams, have been critical in controlling the spread of the virus in complex humanitarian settings.

Safety and side effects

Clinical trial data and widespread field use indicate the vaccine has a favorable safety profile. Common adverse reactions are generally mild to moderate and transient, including injection site pain, headache, fatigue, muscle pain, and fever. These reactions typically resolve within a few days. Ongoing pharmacovigilance is conducted by Merck & Co., national regulatory authorities, and the World Health Organization's Global Advisory Committee on Vaccine Safety. The benefits of vaccination in preventing the high mortality of Ebola virus disease in outbreak settings are considered to far outweigh the risks associated with these temporary side effects.

Category:Viral vector vaccines Category:Ebola Category:World Health Organization essential medicines