Mpox (Formerly Monkeypox) Vaccines

The JYNNEOS (Imvamune or Imvanex) vaccine, made by Bavarian Nordic A/S, is approved in Canada, Europe, and the United States for the prevention of smallpox and mpox. The JYNNEOS vaccine features an attenuated (weakened) form of live vaccinia virus that is incapable of replicating. NIAID provided significant support in the development of JYNNEOS™ as an alternative to the Dryvax and ACAM2000 smallpox vaccines, which can cause severe side effects in people with weakened immune systems and individuals with eczema. In particular, NIAID provided support for the vaccine’s preclinical evaluation through Phase 2 clinical trials. NIAID-funded studies evaluated the vaccine’s safety, immunogenicity, duration of protection and route of administration; the Biomedical Advanced Research and Development Authority (BARDA), part of the U.S. Department of Health and Human Services, supported the advanced clinical evaluation of the vaccine. The U.S. Food and Drug Administration approved JYNNEOS in 2019 for individuals at high risk for smallpox or mpox infection.

Additionally, NIAID supported nonhuman primate studies to determine the effectiveness of vaccination when administered concurrently with the smallpox treatment tecovirimat. Researchers found that that the immune responses induced by the JYNNEOS vaccine or the ACAM2000 smallpox vaccine were not significantly affected by concomitant treatment, and the animals were protected against mpox.

Each of the three vaccines approved for smallpox may also be used to prevent disease in individuals who have been exposed to mpox provided the vaccine is administered as soon as possible after the exposure.

In August 2022, the FDA authorized for emergency use intradermal delivery of JYNNEOS, which is usually administered subcutaneously. Intradermal delivery uses a lower dose to induce a similar immune response and can therefore be a dose-sparing option. NIAID supported previous research evaluating intradermal administration of JYNNEOS and is gathering more data about intradermal delivery and its potential side effects in an open-label clinical trial

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