Generally only infants are vaccinated for pertussis. The vaccine only provides immunity for several years if there is no revaccination. So, people older than elementary age generally have no immunity to it unless they have been revaccinated, but revaccination of older children is not included in the standard vaccination schedule. People who actually get pertussis though are typically immune for 30+ years.
Untrue. Kids get revaxed before they start school at age 4 or 5, and again in Junior high.
As for adults, any time you get a ‘tetanus shot’, it’s now a TDaP complete with pertussis as well.