Effectiveness of Pneumococcal Conjugate Vaccines Against Community-acquired Alveolar Pneumonia Attributable to Vaccine-serotype Streptococcus pneumoniae among Children

Introduction: Streptococcus pneumoniae is a leading cause of pneumonia among children. However, owing to diagnostic limitations, the protection conferred by pneumococcal conjugate vaccines (PCVs) against pediatric pneumonia attributable to vaccine-serotype pneumococci remains unknown. Methods: We analyzed data on vaccination and nasopharyngeal pneumococcal detection among children <5 years old with community-acquired alveolar pneumonia (CAAP; "cases") and those without respiratory symptoms ("controls"), who were enrolled in population-based prospective surveillance studies in southern Israel between 2009 and 2018. We measured PCV-conferred protection against carriage of vaccine-serotype pneumococci via the relative risk of detecting these serotypes among vaccinated versus unvaccinated controls. We measured protection against progression of vaccine serotypes from carriage to CAAP via the relative association of vaccine-serotype detection in the nasopharynx with CAAP case status, among vaccinated and unvaccinated children. We measured PCV-conferred protection against CAAP attributable to vaccine-serotype pneumococci via the joint reduction in risks of carriage and disease progression. Results: Our analyses included 1032 CAAP cases and 7743 controls. At ages 12-35 months, a PCV13 schedule containing 2 primary doses and 1 booster dose provided 87.2% (95% confidence interval: 8.1-100.0%) protection against CAAP attributable to PCV13-serotype pneumococci, and 92.3% (-0.9%, 100.0%) protection against CAAP attributable to PCV7-serotype pneumococci. Protection against PCV13-serotype and PCV7-serotype CAAP was 67.0% (-424.3%, 100.0%) and 67.7% (-1962.9%, 100.0%), respectively, at ages 36-59 months. At ages 4-11 months, 2 PCV13 doses provided 98.9% (-309.8%, 100.0%) and 91.4% (-191.4%, 100.0%) against PCV13-serotype and PCV7-serotype CAAP. Conclusions: Among children, PCV-conferred protection against CAAP attributable to vaccine-targeted pneumococcal serotypes resembles protection against vaccine-serotype invasive pneumococcal disease.