Company description
Live vaccines are derived from disease-causing (“wild”) virus or bacteria in a laboratory. These wild virus or bacteria are attenuated, or weakened by repeated culturing in cells in which they do not reproduce very well. As they evolve to adapt to the new environment, they become weaker with respect to their natural host, human beings. For example, the measles virus used today was isolated from a child with measles in 1954. The conversion of wild viruses into attenuated vaccine viruses requires almost 10 years of serial passage using tissue culture media. The resulting vaccine organisms, which retain the ability to replicate and produce immunity, usually do not cause disease. At present, most live attenuated vaccines contain live viruses. Viruses, such as mumps, measles and chickenpox, are simple microorganisms that contain small amounts of genes, so scientists can control their characteristics more easily.
