2.2 Inclusion and Exclusion Criteria
Our meta-analysis is reported in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Statement and had been registered at International Prospective Register of Systematic Reviews (number:CRD42021266458)12. Studies that met the following criteria were included: (1) cross-sectional studies; (2) children and adolescents aged < 19 years; (3) the population are diagnosed as asthma; (4) the background of the study is COVID-19 pandemic.
However, articles had incomplete or unidentified data were excluded, as well as abstracts, reviews, case reports, letters and duplicate publications.