Polio vaccines? Bad example. Whatever good they did in the past, most outbreaks of polio in the world today are triggered by oral vaccine rollouts.

https://www.cdc.gov/mmwr/volumes/70/wr/mm7049a1.htm

https://abcnews.go.com/Technology/wireStory/polio-outbreak-s...

https://abcnews.go.com/Health/wireStory/polio-cases-now-caus...