If you are like me only using phpMyAdmin a few times every year, it can be a good idea and a easy security measure to disable the config when not needed.
You can disable phpMyAdmin by disabling the module configuration:
sudo a2disconf phpmyadmin.conf
sudo /etc/init.d/apache2 restart
Enable it again with:
sudo a2enconf phpmyadmin.conf
sudo /etc/init.d/apache2 restart