Non immunized susceptible diphtheria contacts should receive:
Erythromycin
Penicillin and diphtheria antitoxin
Penicillin, diphtheria antitoxin and DPT vaccine
No treatment is required
Non immunized contacts should receive prophylactic penicillin or erythromycin. They should also be given 1000 to 2000 units of antitoxin and actively immunized against diphtheria. Ref: Park 21st edition, page 151.