JYNNEOS Booster for Monkeypox Prevention
A booster dose of JYNNEOS vaccine is not currently recommended for monkeypox prevention after completion of the standard 2-dose series. According to the most recent evidence, the 2-dose series provides effective protection without the need for additional doses 1.
Current Vaccination Recommendations
The JYNNEOS vaccine is administered as a 2-dose series with doses given 28 days apart. This vaccination approach is supported by multiple lines of evidence:
- The vaccine is licensed as a 2-dose series (0.5 mL per dose subcutaneously or 0.1 mL per dose intradermally) 2, 3
- Completion of both doses is necessary for optimal protection against monkeypox virus infection 4
- Recent data from 2024 indicates that after receiving the complete 2-dose series, additional doses are not currently recommended 1
Vaccine Effectiveness
The effectiveness of the 2-dose JYNNEOS vaccine series has been well-documented:
A case-control study conducted across 12 U.S. jurisdictions showed that the adjusted vaccine effectiveness was:
- 75.2% for partial vaccination (1 dose)
- 85.9% for full vaccination (2 doses) 3
Full vaccination effectiveness was similar across different administration routes:
- 88.9% for subcutaneous administration
- 80.3% for intradermal administration
- 86.9% for heterologous (mixed) administration 3
Duration of Protection
Current evidence suggests that immunity from the 2-dose series is not waning significantly:
Among breakthrough infections in fully vaccinated individuals, the median interval between the second dose and illness onset was:
- 363 days for those who received 2 intradermal doses
- 263 days for those who received 2 subcutaneous doses 1
These disparate time intervals suggest that immunity is not waning in a way that would necessitate a booster dose at this time 1
Breakthrough Infections
While the vaccine is highly effective, breakthrough infections can occur:
- During May 2022-May 2024,271 mpox cases among fully vaccinated persons were reported to CDC from 27 U.S. jurisdictions 1
- These infections are estimated to have occurred in less than 1% of fully vaccinated persons 1
- Importantly, infections among fully vaccinated persons resulted in less severe disease compared to infections in unvaccinated individuals 1
Special Considerations
For laboratory workers or healthcare personnel with potential occupational exposure to orthopoxviruses:
- Historical guidance for those working with vaccinia virus, recombinant vaccinia viruses, or other nonvariola Orthopoxviruses recommended revaccination every 10 years 5
- For those at risk for exposure to more virulent nonvariola Orthopoxviruses (e.g., monkeypox), empiric revaccination every 3 years was considered 5
However, these recommendations predated the current JYNNEOS vaccine and were primarily focused on older vaccinia-based vaccines in laboratory settings.
Safety Profile
The JYNNEOS vaccine has demonstrated a favorable safety profile:
- The most common adverse events are nonserious and include injection site reactions 6
- Serious adverse events are rare in adults 6
- Adverse events are reported at similar rates for both intradermal and subcutaneous administration 6
Conclusion
Based on the most recent evidence, persons recommended to receive the JYNNEOS vaccine should complete the standard 2-dose series, regardless of the route of administration. At this time, additional booster doses are not recommended for monkeypox prevention 1.