I didnt say 20,000 deaths, I said 20,000 deaths or severe reactions. Also 25 years ago, we vacinated only children, a small percentage of our entire population. I was vacinated back in the 50's and havent been vacinated again since then. Also the US population is much larger today than it was back in the 50-60's, therefore a percentage of that larger number leads to a larger total number people POTENTIALLY at risk for adverse effects.
My own thought but there are quite a few people who are more at risk from an immune standpoint today than in the 60's. More people with AIDS/HIV, allergies, chronic fatigue syndrome, etc. These people with immune problems are likely to be more at risk, either from direct immunization or close association with someone that was immunized.
I recall the number from several documents I read the other day when I did a search on Google. I believe it also matched up with a similar number from a Wall Street Journal article.