CDC is updating webpages with the term "mpox" to reduce stigma and other issues associated with prior terminology. This change is aligned with the recent World Health Organization decision.

Interim Clinical Considerations for Use of JYNNEOS and ACAM2000 Vaccines during the 2022 U.S. Mpox Outbreak

Summary of recent changes

What You Need to Know

  • The U.S. national mpox vaccine strategy was announced on June 28, 2022. Multiple federal agencies, including the Administration for Strategic Preparedness and Response (ASPR), U.S. Food and Drug Administration (FDA), National Institutes of Health (NIH), and Centers for Disease Control and Prevention (CDC) are coordinating to implement this enhanced vaccination strategy.
  • This document provides interim guidance regarding use of JYNNEOS and ACAM2000 vaccines during the mpox outbreak that began in the United States on May 17, 2022. This interim guidance is in addition to standard guidance and recommendations for use of these vaccines from CDC’s Advisory Committee on Immunization Practices (ACIP).
  • Two vaccines may be used for the prevention of mpox disease:
    • JYNNEOS vaccine is approved for the prevention of mpox and smallpox. During the current outbreak, JYNNEOS is the main vaccine being used in the United States.
    • ACAM2000 vaccine is approved for immunization against smallpox and made available for use against mpox under an Expanded Access Investigational New Drug (EA-IND) protocol.
  • The standard regimen for JYNNEOS involves a subcutaneous (Subcut) route of administration with an injection volume of 0.5mL. In the context of the current national Public Health Emergency (PHE), an alternative regimen involving intradermal (ID) administration with an injection volume of 0.1mL may be used under an Emergency Use Authorization (EUA).
  • People may be vaccinated after exposure to mpox virus to help prevent mpox disease (i.e., post-exposure prophylaxis).
  • People who are at higher potential for exposure to mpox virus may be offered vaccination to help prevent mpox disease (i.e., pre-exposure prophylaxis).
  • No data are currently available on the clinical efficacy or effectiveness of JYNNEOS or ACAM2000 for mpox disease.  Limited data on performance of JYNNEOS vaccine in the current outbreak are becoming available. Across 32 U.S. jurisdictions, among males aged 18–49 years eligible for JYNNEOS vaccination, mpox incidence was 14 times as high among unvaccinated males compared with those who had received a first vaccine dose ≥14 days earlier
  • Because there are limitations in our knowledge about the effectiveness of these vaccines in the current outbreak, 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.
  • In the United States, there is a large supply of ACAM2000, but this vaccine has more known side effects and contraindications.

Purpose and Scope

This document provides interim guidance for healthcare professionals and public health officials regarding use of JYNNEOS and ACAM2000 vaccines 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. This interim guidance is in addition to existing standard guidance and recommendations for use of these vaccines from CDC’s Advisory Committee on Immunization Practices (ACIP).

Considerations presented in this document are interim guidelines, which are developed in response to emergencies, such as outbreaks and natural or manmade disasters. The term “interim” indicates that CDC developed these guidelines using either expert opinion, indirect evidence, or emerging evidence, and these recommendations might change when additional evidence becomes available. This document is informed by data and considerations from U.S. federal agencies including ASPR, FDA, NIH, and CDC, general best practice guidelines for immunization, other data sources, and expert opinion.