The next step was development of the vaccine itself. The researchers started with an unsuccessful killed-virus vaccine. Next they tried a small amount of live virus in a vaccine, but this method simply gave people rubella. Then they decided on the most difficult technique — an attenuated, or weakened, virus vaccine. One way to attenuate a virus is to culture it repeatedly in nonhost cells. Because man is the host for rubella, the researchers grew the attenuated virus in kidney cells of monkeys, which are similar to those of man. By the seventy-seventh reculture in monkey kidney cells, the virus was sufficiently weakened. Parkman and Meyer used this HPV-77 strain for the vaccine.

Success.

With the permission of the children's parents, physicians administered the vaccine to sixteen test patients at the Arkansas Children's Colony for retarded children. Eight were given the vaccine...