Experimental live tick-borne encephalitis vaccine (Labgat E5 "14" virus clone): volunteers 1 and 2 years after single-dose immunization.

Groups of volunteers given intramuscularly 5 or 6.5 dex or perorally 6.5 dex newborn mouse icLD50 of the plaquesegregated "14" clone of the Langat E5 virus strain (tick-borne encephalitis comples) were followed for periods of 12 and 24-27 months. Circulating specific virus neutralizing antibodies persisted in them in the absence of apparent reaction as evidenced by clinical, electroencephalographic and cerebrospinal fluid findings.