Reviewed and updated: Christine Kerr, MD, and Mary Dyer, MD, with the Medical Care Criteria Committee; December 15, 2022
|Table 10: Mpox Vaccine [a]
|Trade name||JYNNEOS (also called Imvamune or Imvanex)|
|Type of vaccine||Live virus that does not replicate efficiently in human cells|
|Administration||Two subcutaneous injections 4 weeks apart|
|Indication||Approved by FDA for prevention of smallpox or mpox in people ≥18 years old|
|Adverse reactions||Injection site reactions such as pain, swelling, and redness. Vaccination with JYNNEOS will not cause mpox infection.|
|Contraindications||Severe allergy to any component of the vaccine (gentamicin, ciprofloxacin, or egg protein)|
|Immune response||Maximal development of the immune response takes 2 weeks after second dose.|
|No evidence of reproductive harm from animal data. Pregnancy and breastfeeding are not contraindications for vaccination.|
Abbreviation: FDA, U.S. Food and Drug Administration.
Immunization: The Centers for Disease Control and Prevention (CDC) considers people with HIV to be at risk for severe mpox disease and recommends prioritization of those at risk for receipt of the JYNNEOS mpox vaccine [CDC 2022]. Vaccination is used to prevent mpox and as post-exposure prophylaxis; it protects against disease when administered before exposure. If administered after exposure, the vaccine may prevent development or decrease the severity of mpox disease. See CDC Interim Clinical Considerations for Use of JYNNEOS and ACAM2000 Vaccines During the 2022 U.S. Monkeypox Outbreak.
Two vaccines against mpox are currently approved by the U.S. Food and Drug Administration: JYNNEOS (Imvamune or Imvanex) and ACAM2000. Only JYNNEOS is safe for people with HIV. The ACAM2000 vaccine is contraindicated in adults with HIV and their household contacts.
JYNNEOS contains live vaccinia virus, but the virus does not replicate in humans. JYNNEOS is considered safe to use in adults with HIV regardless of viral load or CD4 cell count. No data are available on the effectiveness of available mpox vaccines in this current outbreak.
The safety and immunogenicity of the JYNNEOS vaccine have been evaluated in adults with HIV; however, the immunogenicity is unknown in individuals who are not virally suppressed or who have with CD4 counts ≤200 cells/mm3. Vaccine efficacy may be lower in patients with low CD4 cell counts. However, given the risk of severe illness in immunosuppressed individuals, vaccination is recommended regardless of CD4 cell count and degree of viral suppression.
Vaccine dosing: The CDC recommends the mpox vaccine be given within 4 days of exposure to prevent disease. If given 4 to 14 days after exposure, vaccination may not prevent disease but may reduce symptoms [CDC 2022]. Peak immunogenicity is achieved 2 weeks after the second JYNNEOS dose [Rao, et al. 2022].
Presentation: A high index of suspicion is required because the clinical presentation of mpox disease can vary from a few scattered papules and mild constitutional symptoms to severe illness. Symptoms of mpox may include fever, headache, muscle aches, backache, swollen lymph nodes, moderate to severe pain, exhaustion, and rash that may include painful oral, anal, or genital lesions.
Mortality: Studies of mpox in remote, medically underserved areas of Central Africa have reported mortality of 11% in unvaccinated individuals [Durski, et al. 2018]. People with advanced HIV or who are not virally suppressed may be at risk of severe disease. To date, no deaths have been reported in the United States during the current outbreak.
Transmission: Although many of those affected in the current global outbreaks are men who have sex with men, the virus can be acquired by anyone who has been in close contact with someone with mpox. The virus that causes mpox is transmitted via the following:
- Direct skin-to-skin contact with an infectious rash, scabs, or body fluids
- Exposure to respiratory secretions during prolonged face-to-face contact or intimate physical contact, such as kissing, cuddling, or sex
- Touching objects or fabrics (e.g., clothing or linens) that have been in contact with the rash or body fluids of someone with mpox
- Being scratched or bitten by an infected animal
CDC. Interim clinical considerations for use of JYNNEOS and ACAM2000 vaccines during the 2022 U.S. monkeypox outbreak. 2022 Oct 19. https://www.cdc.gov/poxvirus/monkeypox/considerations-for-monkeypox-vaccination.html [accessed 2022 Oct 25]
Durski KN, McCollum AM, Nakazawa Y, et al. Emergence of monkeypox – west and central Africa, 1970-2017. MMWR Morb Mortal Wkly Rep 2018;67(10):306-310. [PMID: 29543790]
Rao AK, Petersen BW, Whitehill F, et al. Use of JYNNEOS (smallpox and monkeypox vaccine, live, nonreplicating) for preexposure vaccination of persons at risk for occupational exposure to orthopoxviruses: Recommendations of the Advisory Committee on Immunization Practices – United States, 2022. MMWR Morb Mortal Wkly Rep 2022;71(22):734-742. [PMID: 35653347]