Hayflick produced the first oral polio vaccine ever made on his normal human cell strain WI-38. WI-38 is now used for the production of all of the Rubella Virus vaccine used in the Western Hemisphere. WI-38, or new diploid cell strains, are used today for the manufacture of most human virus vaccines produced throughout the world including those for poliomyelitis, rubella, rubeola, varicella, mumps, rabies, adenoviruses and hepatitis A. Over one billion vaccinees have received vaccines produced on WI-38 or foreign versions of Hayflick's original WI-38.