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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.
