According to a CDC MMWR Report, 77% of cases of tetanus in California, USA, occured in heroin drug users:
‘Tetanus in injecting-drug users (IDUs) with no known acute injury comprised 11% of all cases, compared with 3.6% during 1991-1994. None of the IDU-associated tetanus cases occurred among persons who were known to have been vaccinated. Sixty-nine percent of IDU-associated tetanus cases were reported from California, and 77% of these cases occurred in heroin users.’
13% of people in this report had got tetanus after having recieved the primary series of tetanus ciontaining vaccines as babies. Although they said people who had 3 or more adult doses of the shot didn’t get tetanus (they may not have anyway?). Since the vaccine obviously wears off, I wonder why they bother with the baby shots?
Source: MMWR, July 03, 1998 / 47(SS-2);1-13