Short-Lived Neutralizing Antibody Responses to Monkeypox Virus in Smallpox Vaccine–Naive Persons after JYNNEOS Vaccination

• DOI: 10.3201/eid3102.241300
• Publication Date: 2025-01-10T19:01:42Z
• Authors: Kara Phipps; Jennifer Yates; Jessica Pettit; Sean Bialosuknia; Danielle Hunt; Alan P. DuPuis; Anne Payne; William Lee; Kathleen A. McDon...
• Keywords: Monkeypox; Smallpox vaccine

JYNNEOS, a third-generation smallpox vaccine, is integral to monkeypox virus (MPXV) control efforts, but the durability of this modified vaccinia Ankara-Bavarian Nordic (MVA-BN) vaccine's effectiveness undefined. We optimized and used plaque reduction neutralization test (PRNT) with authentic clade IIa MPXV assess antibody responses over 12 months in 8 donors vaccinated 2 doses JYNNEOS. One donor previously received ACAM2000 vaccine; 7 were vaccine-naive. IgG (L1, B5, A33) or (E8, H3, A35) antigens PRNT titers both viruses peaked at weeks postvaccination waned rapidly thereafter naive donors. especially low; no demonstrated 90% reduction. These data indicate need for improved correlates immunity enable MVA-BN studies, given that recent clinical support vaccine efficacy against despite low responses.