Vaccination coverage, beliefs, and attitudes in transplanted children and adolescents: a mixed-methods systematic review

BACKGROUND Vaccine-preventable infectious diseases are a cause of morbidity and mortality in transplanted children. The main objective of this study was to synthesize the available evidence of vaccination coverage in children and adolescents who are candidates or transplant recipients and to analyze beliefs, attitudes, and experiences about vaccination. METHODS // A mixed-methods systematic review was performed (Open Science Framework registration: https://osf.io/auqn3/). Searches were conducted in PubMed/MEDLINE, EMBASE, IBECS and LILACS (from January 2000 to August 2021) and in gray literature. Quan-titative and qualitative studies reported information on coverage, beliefs, attitudes and/or experiences about recommended vaccines in children who are candidates or recipients of solid organ or hematopoietic progenitor transplantation. Quality assessment was undertaken using Mixed Methods Appraisal Tool (MMAT). A narrative synthesis of the studies was carried out. RESULTS // A total of thirty-two studies in thirty-five publications were included. The most studied interventions were vaccines against measles (n=21; 66%) and hepatitis B (n=20; 62%). Vaccination rates showed a high variability for the most represented vaccines (specifically, 2%-100% for measles, 0.4%-100% for hepatitis B, diphtheria-tetanus-pertussis and rubella), with coverages lower than 90% in at least 70% of the studies. The lowest rates were reported in post-transplantation and hematopoietic stem cell transplantation. Only one qualitative study was identified reporting information on beliefs and/or attitudes, although nine quantitative studies explored cognitive aspects. CONCLUSIONS // This review shows a high variability in vaccination coverage in children and adolescents who are transplant candidates or recipients, with rates lower than those recommended. Further studies would be needed to identify beliefs and attitudes about immunization in this context..