My dad remembers from his childhood occasionally seeing houses placed under quarantine for diseases like measles and then at some point thanks to vaccines measles pretty much just stopped being a thing in most of the US. He got his polio and smallpox vaccines back in the day, and has lived to see smallpox eradicated and polio nearly so.

My grandfather was born a couple years after the 1918 flu pandemic, he had a brother born a couple years before him who died in infancy, he never talked about it much but the timing lines up that his brother was likely a victim of that pandemic. It was certainly something he heard talked about in his childhood just as we'll probably keep talking about COVID for years to come, and I think it definitely left an impact on him, he always was wary about passing germs along to his grandchildren, he always warned our parents against kissing us and never did himself, the only time he did was on his literal deathbed (cancer, nothing communicable) when he kissed my sister (in a non-creepy familial way) as probably one of his last conscious acts.

He was never one to shy away from a fight, I would have loved to see the hell he would have raised against anti-maskers if he'd lived another decade or so. There are people his age or older still walking among us. These things aren't even out of living memory, we're barely a handful of generations removed from them.

The chickenpox vaccine was introduced when I was in elementary school. I remember a lot of children's shows when I was growing up having a chickenpox episode where one or more of the main characters would get chickenpox, they'd take oatmeal baths and slather on calamine lotion to ease the itching, their parents would discuss having their friends over to get them infected early and give them immunity, etc. It kind of seemed like it was inevitable that many if not most kids would get chickenpox eventually, and at the time it kind of was. The vaccine was still optional at the time, and I remember a lot of discussion about it not being very effective, but a lot of kids in my age range got it, and the number of kids in my school who got chickenpox was probably in the dozens instead of probably hundreds just a few years earlier.

There have been some missteps along the way, my dad had a small hepatitis scare when a blood test turned up antibodies (though no active infection) likely from exposure from reused vaccine needles when he was in the army. The US did a grave disserve to polio vaccination efforts by using them as a cover to track down bin Laden and increased distrust in the vaccine in the process. There have been cases where vaccines have used ingredients that have proven unsafe, where people have had adverse reactions, etc. but still overall, the fact that I have never met anyone who has had smallpox, polio, or measles and probably never will speaks volumes about how much more good than harm vaccines do when 100 years ago I would almost certainly have known people who had died or left disabled or disfigured by those diseases.