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The Pfizer COVID-19 vaccine has emerged as the most popular vaccine option on social media, despite the Moderna product proving equally safe and effective in clinical trials and real-world studies.Dado Ruvic/Reuters

In early June, family physician Vanessa Redditt and her colleagues in Ontario’s refugee health care community released a new vaccine information sheet with the title, “Pfizer/BioNTech and Moderna COVID-19 vaccines: Is there a difference?”

Translated into 15 languages, the bulletin explained how the two mRNA vaccines are essentially identical, “like two brands of bottled water – the same product but packaged by different companies.”

Dr. Redditt, who practises at the Crossroads Clinic for refugees at Women’s College Hospital in Toronto, drafted the bulletin after discovering that a handful of her patients were reluctant to take the lesser-known Moderna shot.

“I think a lot of it comes from word of mouth,” she said. “If a trusted friend or trusted family member has recommended a specific brand – in this case, Pfizer – that goes so much further than any government website that says mRNA vaccines are the same.”

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Whether it is among social circles or on social media, the Pfizer shot has emerged as the perceived gold standard in mRNA vaccines, despite the Moderna product proving equally safe and effective in clinical trials and real-world studies.

Some Canadian pharmacy chains, including Sobeys and Rexall, say they’ve seen Moderna hesitancy among their customers, while a handful of public-health units in Ontario have reported people walking away from their appointments when they discover a clinic is offering Moderna instead of the shot made by U.S.-based Pfizer and its German partner, BioNTech.

“At one of our mass vaccine sites, we had people who were finding it was Moderna and saying, ‘Oh, never mind, I don’t want that,’ and leaving,” said Kelly Grindrod, the pharmacy lead for the Region of Waterloo’s COVID-19 response. The clinic started posting health care workers at the door to explain why Boston-based Moderna’s product was as good as Pfizer’s.

Until now, the sought-after Pfizer vaccine has been the most widely available in Canada. That’s about to change: Over the next three weeks, Canada is set to receive nearly 9.5 million Moderna shots, one million of them as part of a newly announced donation from the United States. Those doses were expected to land in Canada on Thursday night.

Pfizer, meanwhile, is sending about 7.2 million doses to Canada by the beginning of July.

Over all, the deluge of mRNA vaccines is terrific news for Canada’s fight against the more transmissible coronavirus Delta variant, which was first identified in India. But the shift in predominant suppliers also means that public-health officials and front-line vaccinators will have to redouble their efforts to convince Canadians that both approved mRNA vaccines are created equal. They’ll often be doing so in the context of offering Moderna as a second dose to people who’ve already taken Pfizer, or vice versa.

“The best vaccine for your second dose is the vaccine that is available first,” Ontario Health Minister Christine Elliott said at a news conference Thursday announcing that all adults in the province would be eligible to book a second dose as of June 28.

That message differs slightly from the recommendation of Canada’s National Advisory Committee on Immunization, or NACI, which says that, “individuals who received a first dose of an mRNA vaccine (Pfizer-BioNTech, Moderna) should be offered the same mRNA product for their second dose,” unless the same product isn’t “readily available” or the brand of the first dose is unknown.

NACI on Thursday recommended that people who took the AstraZeneca vaccine for their first dose take an mRNA shot as their booster. Provincial governments had already stopped offering the AstraZeneca product as a first shot because of its connection to a rare but sometimes fatal blood-clotting syndrome.

The roller-coaster ride of recommendations around AstraZeneca is part of what gave rise to vaccine shopping in Canada in the first place, according to Peter Loewen, a professor of political science at the University of Toronto whose research group has been analyzing weekly online surveys on Canadian attitudes toward COVID-19.

As the official advice on who should and shouldn’t take AstraZeneca changed, doctors could no longer tell Canadians to simply take the first shot offered to them. A clear brand hierarchy took shape, Prof. Loewen said, with Pfizer at the pinnacle and AstraZeneca at the bottom.

Moderna, which most often made in the news in Canada because of supply hiccups, was lost in the shuffle.

According to Prof. Loewen’s most recent data, “people say they are 30 points less likely to take an AstraZeneca [shot] than they are Pfizer, and 10 to 15 points less likely to accept Moderna than they are Pfizer.”

It’s difficult to say how often that translates to people turning down a Moderna shot in the real world. Provincial governments aren’t tracking refusals by brand, and some provinces, including Saskatchewan, let people select their brand of mRNA shot when booking, reducing the risk of walkouts.

In Quebec, where as system doesn’t let people choose their type of mRNA shot, the health ministry said 11,569 people have walked away after learning of the brand – a refusal rate of 166 for every 100,000 doses. Those walkouts could include people offered AstraZeneca earlier in the campaign.

Health districts in Montreal and Quebec City reported they have not seen people passing over Moderna because they want Pfizer.

Dr. Redditt of the Crossroads Clinic said that for her refugee patients, finding and getting to a vaccine appointment remains a far greater barrier than hunting for a particular vaccine. But she doesn’t want to see any vulnerable patient miss an immediate chance to be immunized because they’re waiting for Pfizer.

When Dr. Redditt explains that the Moderna and Pfizer shots use the same technology, work the same way, cause similar side effects and are both about 95-per-cent effective at preventing COVID-19 illness after two doses, her patients are usually happy to take Moderna.

“By leveraging trust and relationships,” she said. “I found that I’ve been able to dispel some of the misconceptions quite readily.”

With reports from Les Perreaux and Laura Stone

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