A nurse prepares a dose of the COVID-19 vaccine on Thursday, Dec. 31, 2020, in Wayne, W.Va. (Sholten Singer/The Herald-Dispatch via AP)

The first doses of the Moderna COVID-19 vaccine have arrived in Ottawa, allowing city staff to begin administering the vaccine to residents in high-risk retirement homes.

A joint memo to Council from medical officer of health Dr. Vera Etches and Ottawa's general manager of emergency and protective services Anthony Di Monte says the city received 40 trays of the Moderna vaccine from the Ontario government on Friday, enough for 4,000 doses.

"This is a noteworthy development as, prior to this shipment, our community had only received doses of the Pfizer-BioNTech vaccine," said the memo.

"These Pfizer-BioNTech doses have and will continue to be received by the Ottawa Hospital (TOH), which has the ultra-cold freezer capacity to store them."

Di Monte and Dr. Etches say the city will use the Moderna supply to offer first doses of COVID-19 vaccine to residents living in high-risk retirement homes.

"The timeline for completion of first doses in all of Ottawa's designated retirement homes is dependent on vaccine supply," says the memo. "The city's mobile vaccination teams will be available to assist in the vaccination of retirement homes.

Mayor Jim Watson tweeted that the city will begin vaccinating residents in high-risk retirement homes on Sunday.

The city has received 30,225 doses of the Pfizer-BioNTech vaccine since the middle of December. A total 28,567 doses have been administered to date.

The memo from Dr. Etches and Di Monte notes the Moderna trays are stable for up to a month at regular fridge temperatures and can be stored for up to six months at minus 20C.

More great news to share!

In addition to finishing up the second round of vaccinations for LTC homes in Ottawa, we have received a shipment of the Moderna vaccine.

Starting Sunday, we will be able to begin vaccinating at high risk retirement homes.

— Jim Watson (@JimWatsonOttawa) February 5, 2021

The Pfizer-BioNTech vaccine requires temperatures between minus 70C and minus 80C. Once it's defrosted, it must be used relatively quickly.

The Moderna vaccine arrived as Ottawa Public Health and Ottawa paramedics completed administering the second dose of the COVID-19 vaccine to residents in all 28 long-term care homes.

Both the Pfizer and the Moderna doses require two doses.