Non-specific effects of Pneumococcal and Haemophilus vaccines in children aged 5 years and under: a systematic review

Objective To determine the evidence for non-specific effects of the Pneumococcal and Haemophilus influenza vaccine in children aged 5 years and under. Data sources A key word literature search of MEDLINE, EMBASE, The Cochrane Central Register of Controlled Trials, the European Union Clinical Trials Register and ClinicalTrials.gov up to June 2023. Study eligibility criteria Randomised controlled trials (RCTs), quasi-RCT or cohort studies. Participants Children aged 5 or under. Study appraisal and synthesis methods Studies were independently screened by two reviewers, with a third where disagreement arose. Risk of bias assessment was performed by one reviewer and confirmed by a second. Results were tabulated and a narrative description performed. Results Four articles were identified and included in this review. We found a reduction in hospitalisations from influenza A (44%), pulmonary tuberculosis (42%), metapneumovirus (45%), parainfluenza virus type 1-3 (44%), along with reductions in mortality associated with pneumococcal vaccine. No data on the Haemophilus vaccine was found. Conclusions and implications In this systematic review, we demonstrate that there is a reduction in particular viral infections in children aged 5 years and under who received the 9-valent pneumococcal conjugate vaccine which differ from those for which the vaccine was designed to protect against. While limited studies have demonstrated a reduction in infections other than those which the vaccine was designed to protect against, substantial clinical trials are required to solidify these findings. PROSPERO registration number CRD42020146640.