Streptococcus pneumoniae is a major cause of disease in older adults, for which two vaccines, a polysaccharide vaccine (PPSV23) and a glycoconjugate vaccine (PCV13), are available. Both vaccines have shown efficacy but differ in their ability to protect against nasopharyngeal carriage and noninvasive pneumonia. Here, Davies et al. used systems serology to compare immune responses to the two vaccines head to head. They observed differences in antibody titers, durability, and antigenic breadth in individuals vaccinated with PPSV23 and PCV13. The authors also found that serum from individuals vaccinated with PCV13 had a wider array of antibody functions. Together, these results characterize differences in vaccine responses that may explain their differential clinical effects.
