The overall course of the COVID-19pandemic in Western countries has been characterized by complex sequences of phases. In the period before the arrival of vaccines, these phases were mainly due to the alternation between the strengthening/lifting of social distancing measures, with the aim to balance the protection of health and that of the society as a whole. After the arrival of vaccines,this multi-phasic character was further emphasized by the complicated deployment of vaccination campaigns and the onset of virus’ variants.To cope with this multi-phasic character,we propose a theoretical approach to the modeling of overall pandemic courses, that we term multi-period/multi phasic, based on a specific definition of phase.This allows a unified and parsimonious representation of complex epidemic courses even when vaccination and virus’ variants are considered, through sequences of weak ergodic renewal equations that become fully ergodic when appropriate conditions are met. Specific hypotheses on epidemiological and intervention parameters allow reduction to simple models. The framework suggests a simple, theory driven,approach to data explanation that allows an accurate reproduction of the overall course of the COVID-19 epidemic in Italy since its beginning (February2020) up to omicron onset, confirming thevalidity of the concept.
Multiple pandemic waves vs multi-period/multi-phasic epidemics: Global shape of the COVID-19 pandemic
Manfredi, Piero
2024-01-01
Abstract
The overall course of the COVID-19pandemic in Western countries has been characterized by complex sequences of phases. In the period before the arrival of vaccines, these phases were mainly due to the alternation between the strengthening/lifting of social distancing measures, with the aim to balance the protection of health and that of the society as a whole. After the arrival of vaccines,this multi-phasic character was further emphasized by the complicated deployment of vaccination campaigns and the onset of virus’ variants.To cope with this multi-phasic character,we propose a theoretical approach to the modeling of overall pandemic courses, that we term multi-period/multi phasic, based on a specific definition of phase.This allows a unified and parsimonious representation of complex epidemic courses even when vaccination and virus’ variants are considered, through sequences of weak ergodic renewal equations that become fully ergodic when appropriate conditions are met. Specific hypotheses on epidemiological and intervention parameters allow reduction to simple models. The framework suggests a simple, theory driven,approach to data explanation that allows an accurate reproduction of the overall course of the COVID-19 epidemic in Italy since its beginning (February2020) up to omicron onset, confirming thevalidity of the concept.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
