Safety and immunogenicity of pneumococcal protein vaccine candidates: Monovalent choline-binding protein A (PcpA) vaccine and bivalent PcpA-pneumococcal histidine triad protein D vaccine

► Pneumococcal PhtD and PcpA vaccine candidates were safe in adults. ► PhtD and PcpA vaccine candidates were immunogenic at 10 μg, 25 μg, and 50 μg. ► PhtD and PcpA provide targets for pneumococcal vaccines.