WINDSOR, ONT. -- Windsor’s medical officer of health is setting the record straight on vaccine interchangeability after concerns were raised about the effectiveness of ‘mixing-and-matching’ two different doses of an mRNA vaccine.

“They should feel comfortable that regardless of whether you’re getting the second dose of the same mRNA or a different mRNA, these vaccines are equally effective,” said Dr. Wajid Ahmed of the Windsor-Essex County Health Unit.

Health Unit CEO Theresa Marentette told reporters Wednesday that as vaccine supply of Moderna increases, “it is likely that people who received Pfizer or AstraZeneca as well, that they could be getting a second dose of Moderna.”

“We may have to interchange them, and that is completely acceptable and that is what we plan to do,” Marentette said.

Dr. Ahmed’s comments about the effectiveness of interchanging vaccines come on the heels of an AM800 interview with Windsor Mayor Drew Dilkens on The Morning Drive with Lisa Williams and guest co-host, Leah Hansen.

Dilkens pointed to the major influx of Moderna vaccine — and questioned what that will mean for people who received a first dose of the Pfizer vaccine.

“The problem is we don’t have seven million people who had first doses of Moderna,” the mayor said. “So now it puts us in a mix-and-match situation.”

Dilkens said he’s hearing from constituents who are unsure whether it’s safe to mix-and-match different mRNA brands, citing U.S. Centres for Disease Control recommendations that advise against mixing first and second doses.

“It’s all to morph and suit the circumstances, which is we didn’t have enough supply in the beginning,” said Dilkens, pointing to the slow roll out of vaccines in the early-going of vaccine acquisition. Today, 75 per cent of adults in Windsor-Essex have received their first dose and 25 per cent have had their second shot.

“I’m not a scientist and I just have my own opinion. And my opinion is I’ve had the first dose of one drug, and I’m going to wait till I can get the same drug as a second dose,” Dilkens said.

He believes the change might cause “a little bit of hesitancy here from people who are just willing to wait it out a little bit to get their second.”

Dr. Ahmed says these messages create doubt in people’s minds.

“Anyone who’s not even a doctor, forget it. I think they shouldn’t even be talking about it,” Ahmed said. “When these doubts are implanted in people’s mind there will be hesitancy, there will be reduced uptake.”

Ahmed said the National Advisory Committee on Immunization and the Public Health Agency of Canada, along with public health professionals all agree that mixing first and second doses is safe, based on evolving science — and that he supports the guidance from the advisory bodies in Canada.

“We should stick to the science and we should stick to the scientific facts, rather than thinking about any kind of policy decisions or any kind of decision that is not based on science,” said Ahmed, hinting the change could happen at Windsor’s mass vaccination sites as early as next week.

He also confirmed that primary care providers and pharmacies are already offering mixed first and second doses.

“If and when we switch it all in the mass vaccination clinic next week (to mixed doses), people should feel comfortable, people should feel confident that we’re not compromising on the safety and effectiveness of the vaccine.”