Ender dragon Kill Nearby ghast fireballs

Okay i try with this execute as @e[type= minecraft:ender_dragon] run kill @e[type= minecraft:fireball,distance=..4] I am trying to make ender dragon inmune to fireballs because my end has ghasts with explosionpower 8 and i dont want ghasts killing the dragon (also if there ir another way to prevent this please help me)