The article presents a summary of the research results of the project on the development of the COVID-19 pandemic in Poland in its initial phase (March-June 2020). It argues that the design and timing of regulatory responses, as well as the adherence of the population to the relevant rules, had a critical impact on the progression and public health consequences of the pandemic. On that basis, the article concludes that well-designed public health measures, which are implemented early as a part of the proactive strategy that anticipates and reacts quickly to changing circumstances can effectively decrease number of COVID-19 infections and related deaths, provided that adherence of a relevant population is high.