P-1655. Anti-Spike IgG4 and Fc Effector Responses: The Impact of SARS-CoV-2 Vaccine Platform–Specific Priming and Immune Imprinting

Abstract Background Repeated mRNA SARS-CoV-2 (COVID) vaccination results in large increases in anti-spike (S)-specific IgG4, but this does not occur after repeat vaccination with Matrix-M®-adjuvanted recombinant SARS-CoV-2 S (rS) protein (NVX-CoV2373, Novavax). The clinical relevance of vaccine-induced anti-S IgG4 and its possible reversal remains poorly understood but may be pivotal for this and other future vaccine targets.Figure 1:Serum anti-Spike IgG4 concentrations (ng/mL) measured by ELISA. A. Comparison of mRNA vaccine primed 3x (gray) and protein vaccine primed 3x (dark blue) followed by protein vaccine boost subject sera. B. protein vaccine primed 2x subject sera followed by mRNA boost. ****p