Phase 3 Trial to Evaluate the Safety, Tolerability, and Immunogenicity of V114, a 15-Valent Pneumococcal Conjugate Vaccine, Followed by 23-Valent Pneumococcal Polysaccharide Vaccine 6 Months Later, in At-Risk Adults 18–49 Years of Age (PNEU-DAY): A Subgroup Analysis by Baseline Risk Factors