How many doses of monkeypox (Orthopoxvirus) vaccine, such as Jynneos (Modified Vaccinia Ankara), are recommended?

Monkeypox (Orthopoxvirus) Vaccine Dosing Recommendations

JYNNEOS vaccine requires two doses administered 4 weeks apart for complete protection against monkeypox. 1

Vaccine Administration Details

JYNNEOS (Modified Vaccinia Ankara vaccine) is the preferred vaccine for monkeypox prevention and is administered as follows:

• Standard dosing regimen: Two 0.5 mL doses administered subcutaneously, 4 weeks (28 days) apart 1
• Administration site: Preferably into the upper arm 1
• Storage: Once thawed, the vaccine may be kept at +2°C to +8°C for up to 4 weeks 1

Route of Administration Options

During the 2022 monkeypox outbreak, an alternative dosing strategy was authorized under Emergency Use Authorization (EUA):

• Standard (subcutaneous): 0.5 mL per dose for all eligible recipients
• Alternative (intradermal): 0.1 mL per dose for adults ≥18 years to expand vaccine supply 2

Both administration routes require the complete two-dose series for optimal protection.

Importance of Completing the Series

Completing the full two-dose series is critical for several reasons:

• Among 496,888 persons who received a first dose during the 2022 outbreak, only 57.6% received their second dose 3
• Two doses provide optimal protection against monkeypox infection 4
• Recent data shows that infections after vaccination were reported in <1% of fully vaccinated persons 4
• Breakthrough infections tend to be less severe in fully vaccinated individuals compared to unvaccinated persons 4

Special Considerations

For Immunocompromised Individuals

• JYNNEOS is a live, replication-deficient modified vaccinia Ankara vaccine that is safe for household contacts of immunocompromised patients 5
• Unlike ACAM-2000 (another smallpox/monkeypox vaccine), JYNNEOS does not pose a risk of unintentional vaccinia transmission to immunocompromised contacts 5
• Immunocompromised persons may have a diminished immune response to JYNNEOS 1

Safety Profile

• Most common adverse reactions are injection site reactions (pain, redness, swelling) 1
• Systemic reactions include muscle pain, headache, and fatigue 1
• Serious adverse events are rare in adults 2
• No serious adverse events have been identified among persons aged <18 years 2

Clinical Pearls

• No additional doses beyond the two-dose series are currently recommended, even for high-risk populations 4
• The Advisory Committee on Immunization Practices (ACIP) recommends JYNNEOS for persons aged ≥18 years at risk for mpox during an outbreak 6
• If administering other vaccines, JYNNEOS can be given simultaneously with most inactivated vaccines 5
• However, JYNNEOS and varicella vaccine should be separated by at least 4 weeks to avoid confusion in identifying the source of any post-vaccination skin lesions 5

Common Pitfalls to Avoid

• Incomplete vaccination: Failure to receive the second dose significantly reduces protection 3, 4
• Improper storage: Once thawed, do not refreeze the vaccine 1
• Incorrect administration technique: Ensure proper subcutaneous (or intradermal if authorized) injection technique
• Inadequate monitoring: Recipients should be observed for at least 15 minutes after vaccination to monitor for immediate adverse reactions 1

Remember that vaccination is most effective when the complete two-dose series is administered according to the recommended schedule.