Retrospective Analysis of an SIR Model Approach to Evaluate Vaccination Strategies in Early Pandemic Prevention

During the 2020–2021 period, increasingly complex models have been developed to understand the impact of containment measures, to predict pandemic trends, and then to optimally allocate the few vaccines available. The objective of this study is to demonstrate the application of a time-varying age-dependent SIRD model for developing a vaccination strategy and for better allocating resources. We used a time-varying age-dependent SIRD model to identify the best vaccination strategy considering the percentages of each age group to be vaccinated. Italian public data were used to estimate the model and perform simulations. Simulations were carried out every 15 days from 27 December 2020 to 27 June 2021. Our projections suggest vaccinating those over 89 before other age groups, following a decreasing pattern, to minimise deaths. The cost function of infected individuals returns more unstable results. In general, to minimise infected individuals, it is necessary to assign vaccines to the over-89 and under-30 age groups. Optimal allocation of the limited available vaccine dose is useful to mitigate transmission and to reduce the mortality associated with it. The application of the mathematical model can be very useful at the beginning of an epidemic caused by a new pathogen, a time when it is important to make optimal use of scarce resources, such as vaccines, to best limit the epidemic by using a standardised approach.