Experimental data on the effectiveness of two schedules of vaccination against human acute encephalomyelitis, one conventional, using 12 injections, and another shortened, using 8 injections, are presented. The experiments in inbred mice evaluating the general resistance, virus-neutralizing antibody titres, resistance in adoptive transfer tests, and values of lymphocyte blastogenesis test showed no statistically significant differences between the shortened vaccination schedule and the conventional one. Experimentally, the shortened vaccination schedule is as effective as the conventional one.