How is the varicella vaccine made?
Like the MMR vaccine, the varicella vaccine is a live, “weakened” form of natural varicella virus. The varicella vaccine virus is “weakened” by a process called “cell-culture adaptation.” (see How Are Vaccines Made?). “Cell-culture adaptation” modifies natural varicella virus so that it behaves very differently once it is injected into the body. Natural varicella virus normally grows in cells that line the skin or the back of the throat. Cells are the building blocks of all the different parts of the body, like skin, heart, muscles and lungs. Natural varicella virus reproduces itself thousands of times, occasionally causes severe disease, and is passed on to the next person unchanged. But the process of “cell-culture adaptation” changes all of that. Natural varicella virus was first taken from a young child infected with varicella in Japan. The family name of the child was Oka and the strain of vaccine virus is now called the “Oka” strain. The virus was then “grown” in human embryo fib