Ear irrigation is a routine procedure used to remove excess earwax, or cerumen, and foreign materials from the ear. The ear naturally secretes wax to protect and lubricate the ear as well as to keep debris out and hinder bacterial growth.
You can't prevent earwax. It's there to protect your ears from dirt and germs.
But you can keep using eardrops to soften the wax. This will help it fall out on its own and should prevent blocked ears.