Vaccine

A vaccine to treat the common cold was used as early as the 20th century before being lost in the Primal Wars. (TV: The Ark)

While on Ashtallah, the First Doctor developed a vaccine to cure the Ashtallans who were dying from a sample of Barbara Wright's blood, noting that his people had long since mastered the science. (AUDIO: The Invention of Death) He later synthesised another from animal membranes to combat an outbreak of the common cold aboard the Ark. (TV: The Ark)