The chickenpox vaccine was first developed in the early 1970s by Dr. Michiaki Takahashi in Japan, who announced the development of the vaccine in 1974. However, the vaccine first became commercially available in 1984. In the United States, it was licensed for use by Merck under the brand name Varivax in 1995, which is when it started to be routinely recommended and widely used. Since the introduction of the vaccine in 1995 in the U.S., chickenpox cases have declined by over 97%.