Kristina's right, but I'd also add this caveat:
As long as they've had a vaccination after the microchipping AND YOU HAVE THE PAPERWORK SHOWING WHEN EACH OF THESE STEPS OCCURRED then they are fine.
When I went to get my paperwork certified by the USDA vet (the last step before tick and tapeworm then departure!), she specifically wanted to see the paperwork/receipts from the microchipping and vaccine, even though the information (dates, times, chip numbers, vaccine batch numbers) were all on the third-country health form as well as the EC 998/2003 form. I just had a computer print-out receipt from the vet that said something like
vet's name
my name
date
microchipping - Toby .......................$cost
rabies vaccination - Toby ..................$cost
microchipping - Xander ....................$cost
rabies vaccination - Xander ...............$cost
$total cost
(paid with mastercard)
and that seemed to be fine, but she asked for it specifically and I got the distinct feeling that if I hadn't had it, I'd have been in trouble.
In short, if you've got documentation that shows the date your doggies were chipped as well as documentation of the date of their latest rabies vaccine, then you should be fine. If you don't have any documentation of the chipping procedure, or your rabies certificate doesn't list the chip number, then you may be better off scheduling another vaccination before you do the blood draw, as they're very strict about the idea that the chip should be read (and that this fact should be documented) at every. single. point.
Good luck with everything!