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JYNNEOS (also known as IMVANEX, IMVAMUNE, and Modified Vaccinia Ankara-Bavarian Nordic [MVA-BN]) is a smallpox vaccine produced by Bavarian Nordic that is also used for monkeypox.

JYNNEOS is the US name of the smallpox vaccine, Modified Vaccinia Ankara-Bavarian Nordic (MVA-BN), also known as IMVANEX in Europe and IMVAMUNE in Canada. This smallpox vaccine made by Bavarian Nordic is a live non-replicating virus. Bavarian’s smallpox vaccine is approved in the US and Canada for monkeypox. In Europe, the vaccine is approved for smallpox but used off-label for monkeypox.

JYNNEOS is one of two vaccines available for smallpox as of May 2022. The other, ACAM2000, contains live replication-competent vaccinia virus and is used to vaccinate military recruits. As of May 31, 2022, Jynneos was the only vaccine approved for monkeypox, which is related to smallpox.Jynneos was offered to higher-risk contacts of people with monkeypox virus in the UK in a ring vaccination strategy where only close contacts are initially immunized. The ring expands if more people need the vaccine. On May 23, 2022, US health officials from the CDC stated they were releasing Jynneos vaccine doses for use in monkeypox cases.

The virus in the JYNNEOS/IMVANEX/IMVAMUNE/MVA-BN vaccine is derived from poxvirus Chorioallantois Vaccinia virus Ankara (CVA), which was attenuated to the version called Modified Vaccinia Ankara (MVA) virus. Ankara is the name of the city in Turkey where the original viral strain came from. After propagation of the virus in the laboratory in chicken embryos, the virus lost the ability to reproduce in most mammalian cells but can still produce an immune response against smallpox. Bavarian Nordic further attenuated MVA to generate MVA-BN. MVA-BN is unable to replicate in a vaccinated individual, which is in contrast to the original smallpox vaccines. Since the replication cycle of the virus is blocked at an early stage, new virus copies are not generated and released in the body. This means that a vaccinated person cannot spread the virus to others.

FDA approval of JYNNEOS for smallpox JYNNEOS is based on twenty-two clinical trials, including two Phase 3 studies. The Phase 3 studies showed that JYNNEOS was not inferior to the smallpox vaccine ACAM2000 in terms of immunogenicity. FDA approval of JYNNEOS for monkeypox was based on survival data in non-human primates challenged with lethal doses of monkeypox virus, which showed 80-100% overall survival with JYNNEOS vaccine compared with 0-40% in control animals. Jynneos is associated with fewer side effects compared with ACAM2000.


May 21, 2022
Multi-country monkeypox outbreak occurs in non-endemic countries
May 18, 2022
USD$119 million option is exercised for the manufacturing of freeze-dried JYNNEOS® in 2023 and 2024.
November 14, 2019
Phase 3 Efficacy Trial of Modified Vaccinia Ankara as a Vaccine against Smallpox.
September 2019
The US FDA approved JYNNEOS™ (Smallpox and Monkeypox Vaccine for prevention of smallpox and monkeypox disease

Further Resources


Bavarian Nordic Announces U.S. FDA Approval of JYNNEOSTM (Smallpox and Monkeypox Vaccine, Live, Non-replicating) for Prevention of Smallpox and Monkeypox Disease in Adults

Bavarian Nordic A/S


September 24, 2019

Safety and Immunogenicity of Modified Vaccinia Ankara-Bavarian Nordic Smallpox Vaccine in Vaccinia-Naive and Experienced Human Immunodeficiency Virus-Infected Individuals: An Open-Label, Controlled Clinical Phase II Trial

Edgar Turner Overton, Jack Stapleton, Ian Frank, Shawn Hassler, Paul A Goepfert, David Barker, Eva Wagner, Alfred von Krempelhuber, Garth Virgin, Josef Weigl, Thomas Peter Meyer, Jutta Müller, Nicole Bädeker, Robert Grünert, Philip Young, Siegfried Rösch, Jane Maclennan, Nathaly Arndtz-Wiedemann, Paul Chaplin



The Brighton Collaboration standardized template for collection of key information for risk/benefit assessment of a Modified Vaccinia Ankara (MVA) vaccine platform

Ariane Volkmann, Anna-Lise Williamson, Heinz Weidenthaler, Thomas P.H. Meyer, James S. Robertson, Jean-Louis Excler, Richard C. Condit, Eric Evans, Emily R. Smith, Denny Kim, Robert T. Chen


May 2021


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