Is it safe to have a 4th CO2 laser if I have erythema after my third session? I had no problems after the first two.

i had 3 CO2 laser sessions for acne scars.first two session reduced the scars appereance(normal radeness only one week).After the third seasion 5 months ago i had redeness that didn't go(laser strength were increased gradually from session to another reaching 14 on 3rd)I need another session, is it safe to do it with this redaness still?i noticed that i no longer get acne in the areas where laser is applied unlike the rest of my face i want to know does laser prevent the acne from appearing?