The original vaccine, composed of whole B. pertussis cells, produced a dramatic decrease in pertussis cases, but sometimes caused severe side effects. It has now been replaced with a newer acellular pertussis vaccine (aP) - McGraw hill Microbio for Health Professionals
Used to be dead bugs (attenuated), now it’s dead bug parts (inactivated), so it’s even safer. That’s why you need the booster though. Attenuated weakened bugs can still replicate, and so they produce a better, longer lasting immunity, but selected antigens can be effective and safer with a booster. The more organized and on board people are, the safer vaccines can be. It’s in places with little trust and scientific knowledge that the attenuated vaccines still have to be used, because you can’t get people to come back for boosters. Same applies to the Salk/Sabin for polio.
