JYNNEOS: The Equivalent to Journavx
JYNNEOS is the equivalent to Journavx (which appears to be a misspelling of Jynneos itself), as they are the same vaccine - a live, replication-deficient modified vaccinia Ankara vaccine used primarily for prevention of monkeypox and smallpox. 1
Vaccine Characteristics and Uses
JYNNEOS is a modified vaccinia Ankara (MVA) vaccine that is:
- FDA-approved for prevention of smallpox and monkeypox in adults aged ≥18 years
- Administered as a 2-dose series, typically 28 days apart
- Available in two administration routes:
- Standard: 0.5 mL subcutaneous injection
- Alternative (under Emergency Use Authorization): 0.1 mL intradermal injection for adults ≥18 years 2
Safety Profile and Key Advantages
JYNNEOS has significant safety advantages over older smallpox vaccines:
- It is replication-deficient, meaning it cannot reproduce in human cells
- Unlike ACAM2000 (another smallpox vaccine), JYNNEOS is safe for household contacts of immunocompromised patients 1
- The most common adverse events are mild and include injection site reactions 2
- Serious adverse events are rare in adults 2
Effectiveness
JYNNEOS has demonstrated strong effectiveness in preventing monkeypox:
- Overall vaccine effectiveness of 75.2% after one dose and 85.9% after two doses 3
- Effectiveness by administration route:
- Subcutaneous: 88.9% effectiveness
- Intradermal: 80.3% effectiveness
- Heterologous (mixed routes): 86.9% effectiveness 3
Clinical Applications
JYNNEOS is recommended for:
- Prevention of monkeypox in high-risk populations
- Prevention of smallpox in case of bioterrorism event
- Risk-based vaccination across all age groups 1
- Can be used in immunocompromised individuals, though effectiveness may be slightly reduced (70.2% vs 87.8% in immunocompetent individuals) 3
Comparison to Other Smallpox/Monkeypox Vaccines
JYNNEOS has important advantages over ACAM2000:
- ACAM2000 is a replication-competent vaccinia virus with risk of unintentional transmission (5.4 events per 100,000 vaccinations) 1
- ACAM2000 has higher risk of serious adverse events including myocarditis and progressive vaccinia 4
- JYNNEOS has a more favorable safety profile with fewer severe side effects 4
Important Considerations for Vaccination
- Complete vaccination requires two doses for optimal protection
- Second dose completion rates have been suboptimal (57.6% in US studies) 5
- Higher second dose completion has been observed among older adults and White persons 5
- Vaccination strategies should address disparities in vaccine access and acceptance
Conclusion
When considering smallpox or monkeypox prevention, JYNNEOS emerges as the preferred option due to its strong effectiveness and superior safety profile compared to alternatives like ACAM2000, particularly for immunocompromised patients or their household contacts 1, 4.