Effects of non-pharmacological interventions as vaccine adjuvants in humans: a systematic review and network meta-analysis

Introduction

Psychological and behavioural factors influence the effectiveness of vaccines. This has led to interest in the potential for non-pharmacological treatments, which modify these factors, to enhance vaccine effectiveness. We conducted a systematic review and network meta-analysis (NMA) to examine the effects of non-pharmacological adjuvants on vaccine effectiveness, as measured by antibody responses to vaccination.

Areas covered

Electronic databases (EMBASE, Medline, PsychINFO, CINAHL) were searched from inception to 6th February 2018. This yielded 100 eligible papers, reporting 106 trials: 79 interventions associated with diet and/or nutrition; 12 physical activity interventions and 9 psychological interventions.

We observed that over half (58/106, 55%) of the trials reported evidence of non-pharmacological interventions enhancing the antibody response to vaccination across one or more outcomes. The NMA considered the evidence for the comparative effects between all intervention types, control and placebo for antibody titres (48 studies), seroconversion (25 studies) and seroprotection (23 studies) separately. The NMA provided only weak evidence in support of nutritional formulae and probiotics in increasing antibody titres.

Expert opinion

This review offers a comprehensive summary of the available literature on non-pharmacological interventions as vaccine adjuvants. The evidence is characterised by considerable heterogeneity but provides early evidence of nutritional formulae and probiotic interventions being associated with enhanced antibody responses to vaccination. The absence of evidence for other treatments may be the consequence of limited and unreliable evidence on these treatments. Large, well-designed studies which include consistent core outcomes and measures of intervention adherence and fidelity are required.