OTTAWA -- A pop-up vaccination clinic in Overbrook has booked up for the day before it was scheduled to open.

The walk-in clinic at the Overbrook Community Centre was scheduled to open at 9 a.m., but people lined up early Thursday morning for the chance to get a shot. Staff handed out appointment cards for all 500 of its doses by around 7:30 a.m.

It was the second such clinic of the week in Overbrook this week. The first one on Tuesday, which was the first walk-in vaccination clinic in Ottawa, handed out appointments for all 500 of its doses in under three hours.

The clinics are part of the city's strategy to vaccinate all adults in high-risk neighbourhoods. There was also a pop-up clinic at the AMA Community Centre on Hunt Club Road Wednesday.

Ottawa Public Health says it is not advertising these pop-up clinics widely, but is instead targeting neighbours in a variety of ways on the ground, including door-knocking, flyers, emails and phone calls with the aid of community partners.

"These clinics will not be promoted widely to the greater public as the intent is to reach individuals in specified areas," OPH said to CTV News Ottawa in a statement this week. "Due to limited vaccine supply, proof of address will be required to ensure eligibility. Community clinics continue and will be advertised broadly."

The city promises it will continue to spread the word within priority neighbourhoods when future pop-up clinics take place.