Waterloo Region Public Health has reported 19 cases of hepatitis A since May.
According to the branch, the region sees on average only six cases per year.
Most of these cases have been associated with drug use, though there are other causes as well.
The virus can be spread by sexual or oral contact, including sharing food or needles.
The vaccine is free for drug users, men who have sex with men, and those with chronic liver conditions.
Lifelong protection can be obtained through a two-dose vaccination.
Over 200 people have been immunized at the clinic since June.
