Pre Omicron and Omicron relationship between COVID-19 incidence and the percentage of cases with unidentified chains of transmissions in Friuli Venezia Giulia, Italy (September 2020-April 2022)

ABSTRACT

Introduction: The study aimed to determine the relationship between COVID-19 incidence and contact tracing quality in Friuli Venezia Giulia Local Health Authorities (LHAs) AS1, AS2, AS3. Materials and methods: Omicron regional prevalence divided the study period (21/09/2020-24/04/2022) into pre Omicron (21/09/2020- 26/12/2021) and Omicron (27/12/2021-24/04/2022). For each sub-period, regional and LHA-specific descriptive statistics on incidence and percentages of cases with unidentified chains of transmissions, household outbreaks and Contact Tracing (CT) quality index (complement of cases with unidentified chains of transmissions/managed cases multiplied by the complement of household outbreaks/active outbreaks, in percentage) were calculated. To investigate the relationship between CT quality index and incidence and between percentage of cases with unidentified chains of transmissions and incidence, regression analysis was performed.