The UK had a very strong pandemic plan (UK Influenza Preparedness Strategy 2011). Other countries adopted it. There was also a simulation exercise (Exercise Cygnus) in 2016 that lasted three days.
FOI requests and legal action have been underway for the last couple of years to find out why much of this was not put into action in early 2020.
Here's one article which focuses on the ventilator shortage, but plenty more can be found.
https://www.newstatesman.com/politic...event-pandemic