Vaccines

Two FDA-approved smallpox vaccines (JYNNEOS and ACAM2000) have been available from the SNS for use as post-exposure prophylaxis (PEP) or pre-exposure prophylaxis (PrEP) for mpox (under the appropriate regulatory mechanism, as applicable). 

JYNNEOS vaccine is FDA-approved for prevention of smallpox and mpox disease. In October 2023, the Advisory Committee on Immunization Practices (ACIP) recommended JYNNEOS for persons aged 18 years and older at risk for mpox: 1) during an mpox outbreak and 2) at risk for mpox because of certain sexual behaviors, expanding eligibility criteria. In addition to the FDA-approved indication for mpox for which JYNNEOS is commercially marketed, JYNNEOS is also authorized under emergency use for additional age groups and alternative routes of administration. Important clinical considerations for providers and healthcare practitioners include: 

• JYNNEOS should be administered as two injections (two-dose series). 
  
• The two doses should be given 28 days apart (range 24-35 days).
  
• If the second dose was not given during the recommended interval, it should be given as soon as possible. 
  
• Peak immunity is anticipated 14 days after the second dose.
• JYNNEOS is indicated for people who are determined to be at high risk for smallpox or mpox infection. The FDA-licensed administration route is subcutaneous (standard regimen) for people 18 years or older. Under an Emergency Use Authorization (EUA) beginning August 9, 2022:
• People younger than 18 years of age determined to be at high risk for mpox disease may receive JYNNEOS via subcutaneous (SC) administration (standard regimen). 
  
• People 18 years of age or older determined to be at high risk for mpox infection may alternatively receive JYNNEOS via intradermal (ID) administration (alternative regimen).
  
• The EUA for JYNNEOS remains in effect, even though the PHE has expired.
• In October 2023, ACIP/CDC recommended vaccination with the 2-dose JYNNEOS vaccine series for persons aged 18 years and older at risk for mpox. 
  
• Early data evaluating the safety and effectiveness of the JYNNEOS vaccine did not identify any new safety concerns and observed a reduction of mpox incidence of 9.6 times among persons who received 2 vaccine doses or 7.4 times among persons receiving 1 mpox dose compared to unvaccinated persons. Vaccine effectiveness ranges from 66-89% for the two- dose series, and 36-75% after one dose. 
  
• JYNNEOS is safe for administration to people with HIV or who have atopic dermatitis.
• JYNNEOS is shipped at -20°C and requires cold chain management.
• When stored at -20°C, labeled expiration date apply.
• Expiration dates are found on the carton but not on the vial itself. 
• Expiration dates may also be found at the ASPR Website for product distributed by HHS.
  
• When thawed and refrigerated at a temperature of 2°C–8°C, unopened vials can be stored for up to 8 weeks based on FDA-issued EUA Fact Sheet for JYNNEOS (this differs, however, from the FDA-approved package insert, which limits storage at 2°C–8°C to 4 weeks).
  
• JYNNEOS is administered with a needle/syringe; SNS does not provide ancillary supplies.

ACAM2000 vaccine is FDA-approved for the prevention of smallpox disease and is allowed under a CDC-held Expanded Access IND for the prevention of mpox disease, particularly for those at occupational risk for orthopoxvirus infections as outlined in the recommendations of the Advisory Committee on Immunization Practices.

More information on these vaccines can be found at: Interim Clinical Considerations for Use of JYNNEOS and ACAM2000 Vaccines during the 2022 U.S. Mpox Outbreak.