I'm sure they will be fine. Look how many strays are out there for God only knows how long and they don't get it...sometimes I think it's luck of the draw.

I talked to our vet about the bi-yearly shots and he too advised against it. Nothing medically, but interceptor controls all of the kinds of worms (except tapeworm) and the shot doesn't...it just works for heartworm and it costs the same amount of money. So, we decided to stay with the pills.

Leslie, call the vet tomorrow and I'm sure they will reassure you. Pssst....I'd be worried too though, so I'm a good one to say don't worry! lol...but...I've never had reason to worry when I did!