If I could go back in time and stop pandemics, there will be better ways to stop the three-year lasting plague.
1. Killing rats. The plague was spread by fleas. However, the structures at that time had hollow spaces between walls. Allowing rats to populate in these conditions. Killing rats will not decrease the number of fleas but spreading will be slower.
2. Blocking houses and city boarders. The only reason why the mask with a bird-like beak worked is because the entire costume was sealed. There should not be any contact with other people. Throughout Europe, quarantine, was developed in the process. However, much later. These places need to be shut down as soon as possible.
3. Wearing masks. Even if the plague was spread by fleas, breaths of the infected people could spread the plague. People in the 21st century are facing horrible air pollution. Allowing people to have mask making process. Since 14th century people dose not have any, mask factories need to be built.
4. For almost all the pandemic to epidemics that occurred before the understanding of the vaccine, there were remedies that also claimed some lives. Proper education about nursing infected people.