Vaccine NMA data & syntax

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. 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 of all trials (k=58/106 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 effects of all intervention types compared with placebo on antibody titres (k=48 studies), seroconversion (k=25 studies) and seroprotection (k=23 studies) separately. The NMA provided weak evidence in support of nutritional formulae and probiotics in increasing antibody titres. This literature provides early evidence of nutritional formulae and probiotic interventions being associated with enhanced antibody responses to vaccination. The absence of evidence for other treatments is likely to be the consequence of limited and unreliable evidence on these treatments.