Pneumococcal conjugate vaccination response in patients after community-acquired pneumonia, differences in patients with S. pneumoniae versus other pathogens

Objectives The goal of this study is to investigate the immune response to the 13-valent pneumococcal conjugate vaccine (PCV13) in former pneumococcal CAP patients. We hypothesize that an impaired or suboptimal humoral immune response against (specific) pneumococcal serotypes might explain the vulnerability for pneumococcal disease. Methods Hospitalised adult CAP patients who participated in two trials (2004–2006 (n = 201) and, 2007–2009 (n = 304)) were screened. Patients eligible for inclusion had CAP caused by either S. pneumoniae (pneuCAP) or due to another well-defined pathogen (otherCAP). Serotype-specific pneumococcal antibody concentrations (total IgG and IgG2/IgG1) before and 3–4 weeks after PCV13 administration were measured (Luminex) and compared between pneuCAP and otherCAP patients. Results We vaccinated 60 patients:i.e. 34 pneuCAP and 26 otherCAP patients. In the pneuCAP group, 74% of patients were categorized as good responders (≥9/13 serotypes with concentration ≥ 1300 ng/ml), versus 77% in the otherCAP group. Significantly fewer full responders (i.e. 13/13 serotypes with a concentration ≥ 1300 ng/mL) were identified in the pneuCAP group (15% vs 42% respectively, p = 0.02). For serotype 1, total IgG and IgG2/IgG1 subset post-vaccination concentrations were significantly lower among pneuCAP patients. Our additional case-series showed that of 16 pneuCAP patients who were infected by a serotype included in PCV13 three patients did not respond against the serotype originally responsible for their CAP episode, including one former bacteraemic pneumococcal CAP patient who also failed to show a response against the serotype responsible for CAP during infection. Thirteen patients did respond to the previously infecting serotype following PCV13 including three patients who had bacteraemic pneumococcal pneumonia and did not show a response during infection against the serotype responsible for CAP. Conclusions Our results confirm the immunogenic properties of PCV13 in former pneumococcal CAP patients including patients previously regarded as potential hyporesponders. A slightly diminished overall humoral response to polysaccharides characterizes the former pneumococcal CAP patients. ClinicalTrials.gov Identifier: NCT02141009.