Hi & Welcome. It is not allowed to consume while taking rabies vaccination. Since alcohol is known to suppress the immunity and the fact that your boyfriend has just started taking the vaccination against rabies, it is therefore not advisable for him to consume alcohol or alcohol containing beverages as they may decrease the efficacy of rabies vaccines. Let him complete the schedule of vaccination as advised by his doctor and to attend the graduation party without consuming alcohol as there are other means of enjoyment apart from taking alcohol. Hope the advice given above would be useful. Kindly rate the answers if you are convinced.