WINDSOR, ONT. -- The first doses of the Moderna COVID-19 vaccine are expected to arrive in Windsor-Essex today.

The region’s first shipment is going to the Windsor-Essex County Health Unit, where it will then be distributed to long-term care homes.

Medical officer of health Dr. Wajid Ahmed says they don’t know the exact amount they will receive, but priority will be for the most vulnerable.

“We may receive enough to vaccinate at least half of the population that are currently residents of long-term care homes and retirement homes and there may be some future supplies that may come to us,” says Ahmed.

Immunizations are expected to begin at the LTC homes and retirement homes on Monday.

The facilities that are being targeted first are not in outbreak. Size of the facility, age and outbreak history are also considered when WECHU is calculating which places to vaccinate first.

“We combine all of those variables together to come up with a composite score to come up with the homes that score high,” says Ahmed.

The vaccine is voluntary, but health officials strongly recommend all eligible recipients get immunized.

“When we are starting at a facility, the plan is to go through all of the residents and vaccinate each one of them before moving onto the next facility,” says Ahmed.

The long-term care staff will continue to go through the current model, which is getting the Pfizer-BioNTech vaccine at St. Clair College. The first Pfizer vaccine was administered in Windsor on Dec. 22.

Some 50,000 doses of the Moderna COVID-19 vaccine are expected to arrive in Ontario Wednesday.

Retired Gen. Rick Hillier, who is leading the province's COVID-19 vaccination program, says the drug will be distributed to long-term care and retirement homes in other regions as well.

Hillier said Tuesday that more than half of Ontarians, about 8.5 million, should receive the vaccine by the end of July.

Ontario's associate chief medical officer of health is expected to discuss the province's framework for vaccine distribution at a news conference this afternoon.

With files from The Canadian Press.