Abstract
The TD97 strain vaccine virus was prepared from the Tanabe strain measles virus by lowβtemperature passages in primary cell cultures and ultraviolet (UV) mutagenesis. The TD97 strain exhibited the following characteristics: highly temperature sensitive, neither multiplying nor forming any plaques at 40Β°C in Vero cells; genetically stable, maintaining high temperature sensitivity after ten successive passages in CE cells at 30Β°C or 35Β°C; and M proteins of this virus about 1 KD slower in mobility in SDSβPAGE than that of the Tanabe strain. The TD97 strain was further confirmed to be attenuated by an inoculation test into primate brain. In field trials, 752 healthy children were inoculated with a live virus vaccine prepared with this strain, and the following results were obtained: the seroconversion rate was 97% (517/533), and the average HI antibody titer was 2^5.2^. An antibodyβincreasing effect was also observed in children who were initially seropositive. In children who seroconverted, the rates of fever were 15.7% (55/351) for 37.5Β°C or higher and 4.0% (14/351) for 39Β°C or higher. The rash rate was 7.7% (27/351), and the incidence of local reaction was 5.4% (19/351). The TD97 strain is thus considered to be suitable in use for an attenuated measles vaccine.