Polio vaccine caused side-effects, up to and including polio.
Every vaccine has carried some level of risk. I do think attitudes on that risk have changed over time though.
(I have a relative who was in the first trials of polio vaccination, and I asked her if there was the same kind of reluctance to get it we were seeing with COVID. She smirked and said "Well, let me think... I was in private school, and we were having an indoor play day that day... Indoor because the plane was gonna fly over to spray the DDT and they didn't want us to get directly dusted... Anyway, no, all our parents wanted us to get it because they all personally knew someone, or someone who knew someone, in an iron lung and didn't want that for their kids").
Every vaccine has carried some level of risk. I do think attitudes on that risk have changed over time though.
(I have a relative who was in the first trials of polio vaccination, and I asked her if there was the same kind of reluctance to get it we were seeing with COVID. She smirked and said "Well, let me think... I was in private school, and we were having an indoor play day that day... Indoor because the plane was gonna fly over to spray the DDT and they didn't want us to get directly dusted... Anyway, no, all our parents wanted us to get it because they all personally knew someone, or someone who knew someone, in an iron lung and didn't want that for their kids").