What will happen if my dog doesn't get his booster?

My two puppies had their first vaccination last january 29, 2018. Their vets scheduled that they're going to have their boosters today (February 12,2018) but they missed it.


Is it alright if they wont get the booster shots anymore? If not, how much time do I still have for me to take them to the vet and get their boosters? :(