The discovery of the polio vaccine.

[GFirmer]

When did the event happen?
1955

Describe what happened.
Dr Jonas Salk and his team at the University of Pittsburgh developed the first polio vaccine by growing samples of poliovirus, and then deactivating it with formaldehyde.

How did this affect the accessibility of the medicine?
This allowed the first world countries to access prevention against poliovirus for the first time in 1966, and third world countries a few years later. It was exciting times and led to a decrease in cases of the virus.

Reference.
https://www.nma.gov.au/defining-moments/resources/polio-vaccine-introduced-in-australia