At what point, when recovering from an illness, should I get a new toothbrush?

I have pneumonia.
I have been on azithromycin for three days, I have two more days on that.
I know that when you are ill, it is probably a good idea to get a new toothbrush, but when do you make the change?
Do you get a fresh brush when you start the antibiotic? Do you change when you finish the antibiotic? When your symptoms are all gone? My toothbrush isn’t old, just a few weeks, and I have a new one at the ready, I just want to change it at the optimal time to get the most benefit.