Prime Minister Mateusz Morawiecki:

By observing everything around us and reading the recommendations of the World Health Organization, as well as through discussions with many of our partners—prime ministers and presidents of other countries—we are making decisions aimed at preventing the spread of the coronavirus. Limiting its social impact, and above all, limiting its impact on public health.

Quote via PAP.

What does this mean?

All mass events have been cancelled. Further steps of this kind cannot be ruled out, such as cancelling classes at universities.