Interim Clinical Considerations for Use of JYNNEOS Vaccine for Mpox Prevention in the United States

Summary of recent changes

Purpose and Scope

These clinical considerations provide information to healthcare professionals and public health officials on use of vaccines for mpox prevention (JYNNEOS and ACAM2000) during the mpox outbreak that began in the United States on May 17, 2022. Considerations apply only to the use of vaccine products in the United States. These clinical considerations are informed by:

  • Recommendations of the Advisory Committee on Immunization Practices (ACIP) and the Centers for Disease Control and Prevention (CDC)
  • Vaccine approval (licensure) under a Biologics License Application (BLA) or authorization under an Emergency Use Authorization (EUA) by the U.S. Food and Drug Administration (FDA)
  • ACIP’s General Best Practice Guidelines for Immunization


  • People at risk of mpox should ideally be vaccinated prior to exposure to monkeypox virus (MPXV).
  • People may be vaccinated after exposure to MPXV to help prevent mpox (i.e., post-exposure prophylaxis).
  • Two vaccines may be used for the prevention of mpox:
    • JYNNEOS vaccine is approved and recommended by CDC and ACIP for the prevention of mpox and smallpox. During the ongoing clade II MPXV outbreak (i.e., outbreak that began in 2022 affecting predominantly gay, bisexual, and other men who have sex with men), JYNNEOS has been the main vaccine used in the United States.
    • ACAM2000 vaccine is approved for immunization against smallpox and could be made available for use against mpox under an Expanded Access Investigational New Drug (EA-IND) protocol. In the United States, there is a large supply of ACAM2000, but this vaccine has more known side effects and contraindications.
  • The standard regimen for JYNNEOS involves a subcutaneous (Subcut) route of administration with an injection volume of 0.5mL. An alternative regimen involving intradermal (ID) administration with an injection volume of 0.1mL may be used under an Emergency Use Authorization (EUA).
    • Both the standard (0.5mL Subcut) and the alternative (0.1mL ID) regimen have been found to be effective for mpox prevention.
    • There is currently adequate supply of JYNNEOS vaccine. Therefore, clinicians can preferentially administer JYNNEOS via the subcutaneous route.
  • JYNNEOS vaccine is licensed as a series of two doses administered 28 days (4 weeks) apart.
  • For people with sexual risk factors for mpox who have not been diagnosed with mpox during the ongoing outbreak or have not already received 2 doses of the JYNNEOS vaccine, CDC routinely recommends vaccination.
  • Administration of additional JYNNEOS vaccine doses (more than 2 doses) is currently not recommended.
  • For those at occupational risk of exposure to orthopoxviruses (e.g., certain research laboratorians*) a booster is recommended at 2-10 years depending on the type of work being performed.
  • People who are vaccinated should continue to take steps to protect themselves from infection by avoiding close, skin-to-skin contact, including intimate contact, with someone who has mpox.

* Research laboratory personnel are those who directly handle cultures or animals contaminated or infected with monkeypox virus (MPXV). Vaccination is not routinely recommended for clinical laboratory personnel who perform routine chemistry, hematology, and urinalysis testing, including for patients with suspected or confirmed MPXV infection, healthcare personnel who care for patients with mpox or administer ACAM2000. Recommended infection prevention and control practices are effective in minimizing transmission. Vaccination can be offered based on site- and activity- specific biosafety risk assessments (e.g., identification of laboratory procedures with a high likelihood of generating aerosols or inadequate PPE availability).


  • On April 1, 2024, Bavarian Nordic commercially launched their JYNNEOS vaccine. During the period immediately following commercialization, HHS will continue to make JYNNEOS vaccine available as needed. The HHS-provided JYNNEOS is intended only as a supplemental supply while commercial availability ramps up, to support access in circumstances in which commercial product is not yet accessible.
  • See the HHS Mpox Vaccine Operational Planning Guide for more information.