Effect of Pneumococcal Conjugate Vaccines on Viral Respiratory Infections: A Systematic Literature Review

Background In addition to preventing pneumococcal disease, emerging evidence indicates that pneumococcal conjugate vaccines (PCVs) might indirectly reduce viral respiratory tract infections (RTIs) by affecting pneumococcal-viral interactions.Methods We performed a systematic review of interventional and observational studies published during 2000-2022 on vaccine efficacy/adjusted effectiveness (VE) and overall effect of PCV7, PCV9, PCV10, or PCV13 against viral RTIs.Results Sixteen of 1671 records identified were included. Thirteen publications described effects of PCVs against viral RTIs in children. VE against influenza ranged between 41% and 86% (n = 4), except for the 2010-2011 influenza season. In a randomized controlled trial, PCV9 displayed efficacy against any viral RTI, human seasonal coronavirus, parainfluenza, and human metapneumovirus. Data in adults were limited (n = 3). PCV13 VE was 4%-25% against viral lower RTI, 32%-35% against coronavirus disease 2019 outcomes, 24%-51% against human seasonal coronavirus, and 13%-36% against influenza A lower RTI, with some 95% confidence intervals spanning zero. No protection was found against adenovirus or rhinovirus in children or adults.Conclusions PCVs were associated with protection against some viral RTI, with the strongest evidence for influenza in children. Limited evidence for adults was generally consistent with pediatric data. Restricting public health evaluations to confirmed pneumococcal outcomes may underestimate the full impact of PCVs. Emerging evidence indicates that pneumococcal conjugate vaccines (PCVs) not only reduce pneumococcal disease burden but also might indirectly reduce viral respiratory tract infections by affecting pneumococcal-viral interactions. We summarized available evidence on PCV protection against virus-related respiratory tract infections in children and adults.