Comparative tests with formolized and irradiated vaccines against leptospirosis.

The effectiveness of gamma-irradiated antileptospirosis vaccines and of vaccines killed with formol was compared in guineapigs. Irradiated vaccines proved no more effective than formolized vaccines in preventing either death or persistent kidney infection. Anti-pomona vaccines gave little protection against serotype icterohaemorrhagiae, and there was no significant difference between irradiated and formolized preparations. Vaccine prepared from a virulent strain showed little advantage over vaccine prepared from weak strains.