Liz Buchanan BVSc MRCVS
Hello! I'm afraid that you need to talk to your vet, who will take guidance from the vaccine company, about this one. The next question might be, 'safe from what?' - as the dog may not be vaccinaed against all 4 Lepto strains and I can't tell without knowing the brand and speaking to the vaccine company (your vet will check this for you) whether they will be functionally vaccinated against any.
However, it is the sort of query that your vet or the vaccination company's vets (your own vet might need to call them) may be able to answer over the phone.
There are sometimes antibody blood tests available o make sure, but sometimes this can be more expensive than simply repeating the Lepto a small number of weeks down the line.