OTTAWA -- Amid attention on what the World Health Organization’s (WHO) chief scientist recently said about mixing and matching COVID-19 vaccines, Prime Minister Justin Trudeau said that Canada’s vaccination strategy is “bearing out,” with increasing take-up and steadily declining new infections.

“Looking at data, looking at how to protect Canadians best, we have taken some strong decisions that quite frankly, are bearing out. We're seeing record numbers of uptake of vaccinations, we're seeing a serious and sustained decline in cases,” Trudeau told reporters on Tuesday.

As of Tuesday, more than 50 per cent of Canadians who are eligible to receive a COVID-19 vaccine have been fully vaccinated against the novel coronavirus. With 68 million doses expected to land by the end of July, Canada is on track to have everyone who is eligible fully vaccinated against COVID-19 by the end of the summer.

According to Chief Public Health Officer Dr. Theresa Tam’s daily statement, across the country new infections continue to decline with an average of 451 cases reported daily during the last seven days.

On Monday, the WHO’s Dr. Soumya Swaminathan issued a caution about citizens opting to receive vaccines from different manufacturers for their first and second, or possibly future booster doses, saying that the data remains limited on the practice and calling it: “A little bit of a dangerous trend.”

“We are in a data-free, evidence-free zone as far as mix and match. There is limited data on mix and match,” she said, cautioning that it could become a “chaotic situation” in countries where citizens decide to take “a second, or a third, or a fourth dose.”

Canadian officials across jurisdictions and doctors quickly spoke out in defence of Canada’s approach, which on the advice of the National Advisory Committee on Immunization (NACI) has recommended AstraZeneca first dose recipients receive an mRNA vaccine for their second dose, while Pfizer and Moderna first dose recipients receive a second shot of either of those mRNA vaccines, if the vaccine they received for their first shot was not readily available.

In a comment to sent Tuesday evening, the Public Health Agency of Canada backed up NACI’s position, pointing to the limited available evidence it did base its guidance on.

“Vaccine interchangeability is not a new concept. Similar vaccines from different manufacturers are used when vaccine supply or public health programs change. Different vaccine products have been used to complete a vaccine series for influenza, hepatitis A, and others,” said the agency in an email.

Swaminathan later clarified that her remark was intended to warn against “individuals mixing and matching vaccines on their own” outside of what public health officials have sanctioned.

The prime minister said Canada’s vaccine strategy—which has been adjusted several times over the course of the rollout to respond to evolving data on adverse reactions and the fluctuating and at time limited vaccine supply—has been based on keeping Canadians safe while delivering as many vaccines as possible, as quickly as possible.

Despite worry that the continually changing COVID-19 vaccine guidance would fuel vaccine hesitancy, among global rankings, after lagging behind for months in early 2021, Canada has one of the largest percentages of the population vaccinated with at least one dose.

Trudeau is among the numerous Canadians who have taken a mixed vaccine regime, receiving a second dose of Moderna on July 2, after first receiving an AstraZeneca dose in April.

At a vaccine clinic in Ottawa Tuesday, most people who CTV News spoke with were comfortable with receiving a mixed dose vaccination regime, saying they are optimistic about the benefits of mixing and the ability to receive their second shots more quickly than they may have been able to if they waited for one shot over the other.

Some, however, walked away from their second dose appointments Tuesday at that Ottawa clinic and another one in Brampton, Ont., after learning the only vaccine available was Moderna, not because of concerns with the vaccine itself but rather citing a desire to have the same type of shot for their second dose.

“We continue to advise Ontarians that mixing of the mRNA vaccines Pfizer and Moderna, as well as mixing AstraZeneca and an mRNA vaccine is safe, it's effective, and it enables people to get their second dose sooner,” said Associate Chief Medical Officer of Health Dr. Barbara Yaffe on Tuesday.

“We are following the advice of the National Advisory Committee on Immunization, which recommends it is safe to mix these vaccines based on studies from the U.K., from Spain, and from Germany. They have found that mixing these vaccines is very safe and produces a strong, effective immune response. Of course, we will continue to monitor the data,” Yaffe said.

“I'm very comfortable immunologically that the best decisions are being made based on the data so far, that this is a safe thing to do. And, we know as much as we know at the moment. This is was an emergency situation where we needed to get this pandemic under control. And therefore, further data will help us if you will, to finesse things as we go forward,” said Dr. Lisa Barrett, an infectious disease expert and assistant professor at Dalhousie University in Halifax in an interview on CTV News Channel.

She said so far the real-world data is showing that mixing is safe and “likely very effective,” and as time goes on more specifics will be known about long-term protection and ideal dosing.

On Tuesday, Trudeau was asked about provinces treating Pfizer and Moderna as interchangeable and whether Canada has received any assurances from countries that will require a proof of vaccination for entry that someone who has received a mixed dose regime will be allowed in.

In response, the prime minister said that work is ongoing to establish what the national standard will be, noting there are other inconsistencies, like Canadians living abroad who have received COVID-19 vaccines in other countries that have not been authorized by Health Canada.

“Our goal is to make sure that as many people as possible are protected as best as possible… And we're going to continue to work with the international community to make sure that people who are fully vaccinated in ways that Canadians recognize as safe and effective, are also recognized around the world,” Trudeau said.