I've read that page previously and again now. No mention of that 98% success rate you were quoting... in fact the opening paragraph states:
"Whooping cough vaccines are effective, but do not last as long as we would like; however, they are still the best way to protect against whooping cough and its complications. "
and this
"There is a decrease in effectiveness in each following year. About 3 or 4 out of 10 people are fully protected 4 years after getting Tdap."
98% effectiveness..? I don't think so. And the truth is they are guessing these numbers, they don't really know.
What this article basically tells you is that you have to keep pumping yourself with the vaccine for the rest of your life, because it's efficacy is shortlived and in some people it's non-existant.
