4 mo sleep regression or sick/shots?

Ever since my babys shots (last week) he gets up at 3 or 4 am and wont go back down to sleep for an hour or 2. It has been every night (usually he goes right back to bed after bottle) then everyone in my house was sick and throwing up about 2 days after his shots!! We are all better now but he is still doing the nighttime thing.. but I'm wondering if this is the 4 mo regression (what are typical signs of the regression for your lo??) or just still not feeling good from being sick?? We are also 1 week away from being out of leap 4!