Background and objective:
Within the worldwide challenge of tackling vaccine hesitancy, the Strategic Advisory Group of Experts on Immunization (SAGE group) strongly fosters vaccination remind or recall interventions that, alongside new opportunities offered by scientific progress, represent key to successfully immunize target population classes. This systematic review with meta-analysis will provide an evaluation of the effectiveness of different remind or recall vaccination interventions in comparison to standard vaccination offer.

Methods:
Two literature databases (PubMed/MEDLINE and Scopus) were consulted in February 2022, retrieving 1850 studies. PRISMA statement guidelines were adopted and 80 manuscripts (47 trial/RCTs, and 33 before–after studies) were included after the assessment phase. Meta-analysis with random-effects model was performed by using STATA software (ver.14.1.2). The selected outcome was the relative risk (RR) of vaccination coverage improvement effectiveness. Furthermore, meta-regression analyses and funnel plots were provided for the included manuscripts.

Results:
The analyses displayed, for cumulatively considered interventions, an overall effectiveness of RR=1.22 (95% C.I.:1.18–1.25, p<0.001) for RCTs and RR=1.70 (95% C.I.:1.54–1.87, p<0.001) for before–after studies. Subgroup analyses allowed to identify “multicomponent” (RR=1.48, 95% C.I.:1.32–1.66, p<0.001) and “remind clinical” (RR=1.25, 95% C.I.:1.17–1.34, p<0.001) interventions as the most effective activities that increased vaccination coverage for RCTs. On the other hand, “education” (RR=2.13, 95% C.I.:1.60–2.83, p<0.001) and “multicomponent” (RR=1.61, 95% C.I.:1.43–1.82, p<0.001) interventions granted highest increase levels for before–after studies. As showed in meta-regression analyses, more effective interventions were carried out among adult-middle-aged population (RCTs: p=0.01, 95% C.I.:0.09–0.61, coeff.:0.51; before–after: p=0.01, 95% C.I.:0.70–1.84, coeff.: 1.27).

Conclusion:
Community, family, and healthcare-based multidimensional interventions, as well as education-based catch-up strategies, effectively improve vaccination coverage. Therefore, their systematic implementation could be utmost relevant to target under-vaccinated population classes, thus aligning with nationally scheduled coverage levels and, ultimately, trying to eliminate or eradicate vaccine-preventable diseases.