Real Infection Spreading Rates for the COVID-19 pandemic in Ukraine estimated with the Use of the Novel Reproduction Number

Two subvariants of the Omicron strains NB.1.8.1 and XFG caused the rapid increase in the number of COVID-19 cases registered in Ukraine in the summer of 2025. In this regard, there is a need for objective estimates of the recent infection spreading rate and its comparison with previous periods of the COVID-19 pandemic. Recently proposed new reproduction numbers enable the estimation of the ratio of the actual number of infected individuals (registered and hidden) at different periods without the need for integration of differential equations and identification of the model parameters. The simple method of calculation was applied without smoothing the weekly datasets. The results for the period 2020–2023 and the summer of 2025 are presented and compared with calculations of the effective reproduction number available in the literature. The new reproduction number and the method for estimating it can be recommended as a simple tool for controlling real epidemic dynamics.