CALGARY -- Alberta Health confirms it will withhold its current supply of the AstraZeneca COVID-19 vaccine for second doses.

In a statement to CTV News, officials said Alberta has approximately 8,400 AstraZeneca doses remaining and there is uncertainty regarding future shipments of the vaccine 

"Alberta has administered approximately 255,000 first doses of AstraZeneca and 2,200 second doses. The remaining supply of about 8,400 doses will be used as second doses," said Tom McMillan, Alberta Health spokesperson in the statement issued Tuesday morning. "Unlike with AstraZeneca, Alberta is receiving the Pfizer and Moderna vaccines in large and consistent shipments. More than 236,000 doses are arriving this week alone.”

Neena Hardman received her first dose of AstraZeneca just over two weeks ago and says this latest decision makes her uncomfortable.

"When I went for my first dose I was under this understanding that my second dose will be available in 12 weeks." said Hardman.

Now she worries if her second dose will be a different vaccine brand.

"I totally believe in science, but not this kind of science where I feel like I’m a guinea pig."

The manufacturer recommended timeframe for a second dose of AstraZeneca is four months. Alberta Health says people are currently eligible for their second dose of AstraZeneca no later than four months — and no earlier than 12 weeks — after the first dose.

McMillan says Alberta Health will continue to monitor the situation and adapt according to supply availability and emerging research. Current recommendations are to have the same vaccine for the first and second doses. 

"This decision is based on the fact that we are receiving no known future shipments of AstraZeneca at this time but are receiving large quantities of mRNA vaccines," said McMillan in his statement. 

The province said vaccine procurement is being led nationally and Alberta Health has not been informed of any additional confirmed shipments of AstraZeneca at this time.

Dr. Eddy Lang, department head of emergency medicine at the University of Calgary Cumming School of Medicine, says there appears to be no definitive evidence as to whether mixing and matching separate vaccine doses is a good idea but says the uncertainty is no reason to delay getting an initial vaccination.

"More important than anything is the idea of getting vaccinated and following current guidelines which for the moment are to make sure your second dose is the same as your first dose."

Lang said patients who have been eligible for a vaccine are ending up in hospitals and some have even died from the virus.

"Getting vaccinated is a top priority for us. As for this particular decision it seems to make a lot of sense that if you’re not sure that you can give everyone their second dose, you need to stop giving people who are eligible their first dose to make sure that you can give all the second doses."

Canada’s chief public health officer is reassuring Canadians anyone who got an AstraZeneca shot that they the right decision to protect themselves and their communities.

"We will make sure that those who got the AstraZeneca vaccine first dose can be provided with a second dose," said Dr. Theresa Tam.

Tam said the government is following evolving science and studies and will determine if there is evidence to suggest doses can be mixed.