» Rubella Virus Vaccine Live conforms to the regulations of the FDA concerning biologics (630.60 to 630.67) (see Biologics 1041). It is a bacterially sterile preparation of live virus derived from a strain of rubella virus that has been tested for neurovirulence in monkeys, and for immunogenicity, that is free from all demonstrable viable microbial agents except unavoidable bacteriophage, and that has been found suitable for human immunization. The strain is grown, for purposes of vaccine production, on primary cell cultures of duck embryo tissue, derived from pathogen-free flocks, or on primary cell cultures of a designated strain of human tissue, provided that the same cell culture system is used as that in which the strain was tested. The strain meets the requirements of the specific safety tests in adult and suckling mice; and the requirements of the tests in monkey kidney, chicken embryo, and human tissue cell cultures and embryonated eggs. In the case of virus grown in duck embryo cell cultures, the strain meets the requirements of the test by inoculation of embryonated duck eggs, and of the tests for absence of Mycobacterium tuberculosis and of avian leucosis. In the case of virus grown in rabbit kidney cell cultures, the strain meets the requirements of the tests by inoculation of rabbits and guinea pigs, and of the tests for absence of Mycobacterium tuberculosis and of known adventitious agents of rabbits. In the case of virus grown in human tissue cell cultures, the strain meets the requirements of the specific safety tests and tests for absence of Mycobacterium tuberculosis or other adventitious agents tests by inoculation of rabbits and guinea pigs and the requirements for karyology and of the tests for absence of adventitious and other infective agents, including hemadsorption viruses and Mycoplasma, in human diploid cell cultures. The strain cultures are treated to remove all intact tissue cells. The Vaccine meets the requirements of the specific tissue culture test for live virus titer, in a single immunizing dose, of not less than the equivalent of 1000 TCID50 (quantity of virus estimated to infect 50 percent of inoculated cultures × 1000) when tested in parallel with the U.S. Reference Rubella Virus, Live.