Abstract: In this update, we found four new studies, for a total of ten studies. We included seven RCTs and three cluster-RCTs involving a total of 4527 participants, although we were unable to pool the data from one cluster-RCT. Three of the ten studies were conducted in low- or middle- income countries. All included studies compared face-to-face interventions with control. Most studies evaluated the effectiveness of a single intervention session delivered to individual parents. The interventions were an even mix of short (ten minutes or less) and longer sessions (15 minutes to several hours). Overall, elements of the study designs put them at moderate to high risk of bias. All studies but one were at low risk of bias for sequence generation (i.e. used a random number sequence). For allocation concealment (i.e. the person randomising participants was unaware of the study group to which participant would be allocated), three were at high risk and one was judged at unclear risk of bias. Due to the educational nature of the intervention, blinding of participants and personnel was not possible in any studies. The risk of bias due to blinding of outcome assessors was judged as low for four studies. Most studies were at unclear risk of bias for incomplete outcome data and selective reporting. Other potential sources of bias included failure to account for clustering in a cluster-RCT and significant unexplained baseline differences between groups. One cluster-RCT was at high risk for selective recruitment of participants. We judged the certainty of the evidence to be low for the outcomes of children's vaccination status, parents' attitudes or beliefs, intention to vaccinate, adverse effects (e.g. anxiety), and immunisation cost, and moderate for parents' knowledge or understanding. All studies had limitations in design. We downgraded the certainty of the evidence where we judged that studies had problems with randomisation or allocation concealment, or when outcomes were self-reported by participants who knew whether they'd received the intervention or not. We also downgraded the certainty for inconsistency (vaccination status), imprecision (intention to vaccinate and adverse effects), and indirectness (attitudes or beliefs, and cost). Low-certainty evidence from seven studies (3004 participants) suggested that face-to-face interventions to inform or educate parents may improve vaccination status (risk ratio (RR) 1.20, 95% confidence interval (CI) 1.04 to 1.37). Moderate-certainty evidence from four studies (657 participants) found that face-to-face interventions probably slightly improved parent knowledge (standardised mean difference (SMD) 0.19, 95% CI 0.00 to 0.38), and low-certainty evidence from two studies (179 participants) suggested they may slightly improve intention to vaccinate (SMD 0.55, 95% CI 0.24 to 0.85). Low-certainty evidence found the interventions may lead to little or no change in parent attitudes or beliefs about vaccination (SMD 0.03, 95% CI -0.20 to 0.27; three studies, 292 participants), or in parents’ anxiety (mean difference (MD) -1.93, 95% CI -7.27 to 3.41; one study, 90 participants). Only one study (365 participants) measured the intervention cost of a case management strategy, reporting that the estimated additional cost per fully immunised child for the intervention was approximately eight times higher than usual care (low-certainty evidence). No included studies reported outcomes associated with parents’ experience of the intervention (e.g. satisfaction). There is low- to moderate-certainty evidence suggesting that face-to-face information or education may improve or slightly improve children's vaccination status, parents' knowledge, and parents' intention to vaccinate. Face-to-face interventions may be more effective in populations where lack of awareness or understanding of vaccination is identified as a barrier (e.g. where people are unaware of new or optional vaccines). The effect of the intervention in a population where concerns about vaccines or vaccine hesitancy is the primary barrier is less clear. Reliable and validated scales for measuring more complex outcomes, such as attitudes or beliefs, are necessary in order to improve comparisons of the effects across studies.

Plain-language summary: We included trials published up to July 2017. We found ten studies with a total of 4527 participants that looked at the effects of face-to-face information or education for parents. Seven studies were from high-income countries, and three were from low- or middle-income countries. The interventions were a mix of short (under ten minutes) and longer sessions (15 minutes to several hours) that were delivered to new or expectant parents. We analysed data on the effects of face-to-face information or education on seven different outcomes. According to the included studies, face-to-face information or education may have improved children’s vaccination status, probably slightly improved parents’ knowledge or understanding of vaccination, and may slightly have improved parents’ intention to vaccinate. These interventions may have led to little or no difference in parental attitudes or anxiety related to the intervention. Only one study measured the cost of a face-to-face case management strategy. In this study, the cost of fully immunising one additional child was eight times the cost of usual care, but the intervention was complex, and the study was older, and not widely generalisable. No studies measured parents’ satisfaction with the face-to-face intervention. We judged the certainty of the evidence to be moderate for parents' knowledge or understanding, but low for all other outcomes. We downgraded the certainty of the evidence where studies were judged to have problems with bias from different sources (e.g. the way in which participants were assigned to study groups), where there was a lot of variability in results or imprecise estimates, or where we had misgivings about the choice of outcomes measures. This review suggests that immunisation-focused educational messages may be sufficient to improve vaccination coverage and, to a small degree, knowledge, particularly where awareness is identified as a barrier to vaccination.