Putting antibiotic ointment inside your nose is safe and can create a barrier for germs and viruses from getting into your body through your nose.
The antibiotic ointment can help prevent the flu at least somewhat because the flu virus and cold virus won't be able to get into your body through your nose.
But you still may get the flu because the flu virus and cold virus can get into your body through your eyes and mouth as well.
Be sure to eat plenty of food with Vitamin C, stay hydrated and wash your hands often to help keep your bodies immune system built up and prevent the spread of germs.
Eating garlic can also boost your immune system which can prevent the flu and cold viruses.