Analysing the COVID-19 epidemic in Italy through the Reed-Frost model: A methodology to delimit epidemic waves over time

Objectives: to set out a method based on the Reed Frost model to delimit over time COVID-19 epidemic waves in Italy. Design: the available national epidemic reports published by the Protezione Civile (Italian civil defence) from 24.02.2020 to 16.022022 were used to collect data on COVID-19 epidemic in Italy. Then, the Reed-Frost model was applied to develop a methodology based on the calculation of the effective contact probability, i.e., the probability of contact. Setting and participants: in Italy, a daily report related to the epidemic was immediately available, including main epidemiological data (point and periodic infection prevalence, mortality, etc), which made it possible for researchers from different institutions to perform analyses about the epidemic. Results: an iterative methodology was developed resulting in the identification of the start-of-wave, end-of-wave, and inter-wave periods and of the starting and ending days of the COVID-19 epidemic waves in Italy (first wave: from 26±2 February 2020 to 28±2 June 2020). Conclusions: this study led to the development of an accessible and reproducible method to determine the start-of-wave and end-of-wave dates of an epidemic, starting only from the number of cases and susceptible people. The main implications of the method mainly consist in allowing benchmarking and forecasting analyses of the epidemic trend to be carried out to support policy and decision-making processes.