A mass vaccination clinic at the Metro Toronto Convention Centre reopened on Monday but only to administer second doses to the 378 healthcare workers who received their first shots at the facility in January.

The city opened the clinic as a part of a “proof of concept” exercise on Jan. 18.

The site had been expected to run for at least six weeks in order to gather data about how best to host vaccination drives in larger settings.

But it had to close after just two days due to a vaccine shortage that resulted from a slowdown in manufacturing at Pfizer’s European plant.

The clinic, however, was back in operation today as workers administer second doses to the individuals who were vaccinated at the site back in January.

It will close at the end of the day on Tuesday.

City officials said last week that all 378 healthcare workers have already been given appointment times and that there will be no opportunity for additional vaccinations at the facility.

“It’s pretty dangerous for myself and my clients,” a client services worker in the city’s shelter system, who was among those receiving their second dose, told CTV News Toronto. “I also want to be a role model to let them know that it’s OK to get the vaccine.”

The city is currently targeting early April for the opening of nine vaccination clinics, including the Metro Toronto Convention Centre site.

That is contingent on the supply of COVID-19 vaccines improving.

“While the vaccine supply and availability issues continue to be worked out between the provincial and federal governments, we will be hard at work here continuing to assemble, build and prepare each of our nine city-operated locations to ensure that they’re set up, that they are ready, that our staffing is in place and that we are ready and able to go as soon as the province can make vaccine available to us,” Fire Chief Matthew Pegg, who is leading the city’s emergency response, told reporters last week. “Our city operated clinics are just one piece of the vaccination plan. There will be many opportunities for vaccination for all Toronto residents once the supply of the vaccine is re-established.”

Ontario has administered more than 476,000 doses of COVID-19 vaccines to date.