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.