[SARS-CoV-2 epidemic among Italians e resident immigrant population: differential incidence from an interregional multicentre study].

Objectives: to describe differences in the incidence of SARS-CoV-2 infections between Italians and foreigners residing in seven Italian Regions during the different phases of the pandemic and by gender.
Design: retrospective observational study.
Setting and Participants: all confirmed SARS-CoV-2 infections from 02.02. 2020 to 16.07.2021 in the seven Regions under study were included. Italian resident population calculated by the National Institute of Statistics as of 01.01.2020 was used to calculate the rates. The considered period is divided into 5 sub-periods (phases).
Main Outcome Measures: number of confirmed SARS-CoV-2 infections in the five phases of the pandemic and crude rates by citizenship (Italian vs foreign). Distribution of infections by age group and by week. Crude and age-adjusted incidence rates ratios (IRR) were calculated, by Region, gender, and phase of the pandemic.
Results: an epidemic curve delay was observed in foreigners in the first phase of the epidemic, in particular in the northern Regions, the most affected in that phase. The first phase of the epidemic was characterized by a greater proportion of cases occurred in people aged over 60 years than the other phases, both in Italians and in foreigners. The incidence among foreigners is higher during the summer of 2020 (intermediate period: June-September 2020) and during the last period (May-July 2021) in all Regions. The overall figure shows a lower incidence among foreigners than Italians, except for males in Tuscany.
Conclusions: the lower incidence rates among foreigners should be interpreted with caution as the available data suggest that it is at least partly attributable to less access to diagnostic tests. Regional differences found in the study deserve further research together with the effect of gender and country of origin.