OTTAWA -- Ontario’s decision to halt administering the AstraZeneca COVID-19 vaccine hit close to home for Tracy Lager, who had just gotten her first shot and has no idea when she’ll get her next one. 

"I don’t know if we’re going to get AZ or Pfizer, Moderna. We’re not sure when, which one and what the effects of mixing them are," Lager said.

The 49-year-old is one of 66,000 Ottawa residents who opted to get the first available vaccine – AstraZeneca.

This week, Ontario announced a pause on administering the first doses of the AstraZeneca vaccine amid concerns over rare but serious blood-clotting incidents.

"It made me really nervous," said Lager. "I have a blood-clotting disorder. My anxiety definitely went into overdrive."

"Anybody who has the AstraZeneca should be vigilant about symptoms especially if they don’t go away," said Dr. Dale Kalina, an infectious disease physician at Joseph Brant Hospital. "We look to a range of four to 28 days."

Dr. Kalina said these are rare risks, but they are treatable.

In Ontario, officials say the risk is one in 55,000. They join a list of other provinces waiting for guidance on what to do with their AstraZeneca supply. But one option is mixing vaccines.

Studies from the United Kingdom so far suggest it is safe. But it does produce more side effects like fatigue, muscle aches and flu-like symptoms. That data is still being studied.

"That data will be produced in a few weeks,” said Dr. Kalina. "We will know if it’s both safe and efficacious and I expect those check marks are given provinces will proceed with using a strategy like that."

For now, Lager is keeping an eye on symptoms, leaving instructions for loved ones around the house.

As for a preference on her second dose, she's not picky.

"If I’m offered AstraZeneca the second shot, I’ll take it."