He has barely been targeted and has allowed only short catches. According to PFF's data --
Week 1 against Green Bay -- allowed 3 of 4 for 25 yards.
Week 2 against San Diego -- allowed 3 of 5 for 25 yards
Week 3 against Baltimore -- allowed 4 of 6 for 13 yards
Ramsey played all but three snaps in those games, against Aaron Rodgers, Philip Rivers and Joe Flacco, who threw 34, 25 and 40 passes, respectively. He allowed 10 catches on 15 attempts (a "burn rate" of 66.7%) -- but only 6.3 yards per catch, 4.2 yards per attempt, 21.0 yards per game and less than 0.65 yards per opponent pass attempt. All of those numbers are very, very good.
I don't have the Week 4 numbers from PFF, but Andrew Luck threw 42 passes for 234 yards (5.6 YPA).