The polio vaccine has been around for 70 years and smallpox vaccination has been around for over 200 years. If you were to assess the polio vaccine a few years after its introduction and compare it to mRNA vaccines a few years after their introduction, then the COVID-19 vaccine might actually come out better. There was a major safety problem with one company's process for manufacturing the initial polio vaccine. 11 children died. If you read contemporary reporting from 1957 - two years after the vaccine was released - you see quotes like this: "The failure of this vaccine to prevent disease and at times death in certain vaccinated individuals and its apparent inability to reduce the number of carriers clearly indicate that polio will not be "wiped out" by this vaccine."

https://www.theatlantic.com/magazine/archive/1957/02/how-goo...