It's both. There's a cluster of "crazy hippy" people in and around Marin who are convinced vaccinations are responsible for every modern ailment. I've met, and tried unsuccessfully to reason with a few of them.

The DTAP booster may be our best shot (haha) at routing around them though. Even if they won't vaccinate their children, if enough adults get regular DTAPs we might be able to get enough herd immunity that whooping cough dies out again.

Apparently that's new: in the US at least, Tdap was only approved in 2005, and replaced Td (the previous standard bundled tetanus/diptheria every-10-years booster) in most recommendations/clinics around 2006-2007. So adults who haven't had a tetanus booster in the past 3-4 years didn't get the one that includes whooping cough, and probably don't even know about the change (I got my last booster in 2003, and didn't know that it was different now).

... And now I understand why my doctor gave me a tetanus booster last month without even asking if I had had one in the last ten years. (I think I have, but I'm not sure, and I never turn down free tetanus boosters if the doctor offers one.)