Guillain-Barré syndrome and SARS-CoV-2 infection: a systematic review and meta-analysis on a debated issue and evidence for the 'Italian factor'.

An increased risk of GBS occurred in northern Italy during early COVID-19 pandemic. The recognition of the 'Italian factor' reconciles contrasting results of the epidemiological studies. The slightly reduced GBS risk in other countries and the relatively high frequency of GBS associated with SARS-CoV-2 infection can be explained by the adopted health measures that decreased the circulation of other GBS infective antecedents.