Diptheria hasn’t been seen in decades, it isn’t because of the vaccine but better sanitation and hygiene.
Tetanus ? If you have it, the shot won’t help you, it takes 3 weeks to take effect. If you have been confirmed that you have tetanus then you want the tentanus shot, —
Pertusis aka Whooping Cough is bacterial, always changing. Doctors have found out that you can shed it (not knowing to others) because it remains in your throat for 28 days. Further because it is bacterial, it is ever changing, it really gives you no protection at all and it doesn’t give you any immunity either.
The largest outbreak was studied by Kaiser in 2010. They found that 81% of the people had either all their DTAP/TDAP doses, 10% had all doses but the last one and the remaining 9% didn’t have any doses at all. The 9% also had it less severe and ended up with something those with the dtap/tdap vaccine couldn’t get immunity.