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Ontario health officials say mixing vaccines 'safe and effective,' warn about rise in COVID cases by Sept.

Last Updated Jul 13, 2021 at 4:38 pm EDT

Ontario’s top health officials are assuring partially and fully vaccinated residents that mixing vaccines is safe and effective, one day after the World Health Organization (WHO) cautioned against the “dangerous trend.” 

Speaking on Tuesday, Associate Chief Medical Officer of Health Dr. Barbara Yaffe says the National Advisory Committee on Immunization’s (NACI) initial recommendation to mix doses was based on several clinical studies from the United Kingdom, Spain and Germany that showed strong immune responses.

“[The] mixing of mRNA vaccines, as well as AstraZeneca and mRNA, is safe and effective and enables people to get their second doses sooner,” said Yaffe.

In mid-June, NACI advised that people who received the AstraZeneca vaccine as their first dose should get Pfizer-BioNTech or Moderna for their second shot.

The WHO’s Chief Scientist, Dr. Soumya Swaminathan, caused confusion and panic after she advised people on Monday that they shouldn’t mix and match COVID-19 vaccines from different manufacturers.

“There is a tendency now for people in countries with enough availability of vaccines to voluntarily start thinking about an additional dose. There are people who are thinking about mixing and matching. We receive a lot of queries from people who say they’ve taken one and they’re planning to take another one. So it’s a little bit of a dangerous trend here,” she said.

“We are in a data-free, evidence-free zone as far as mix and match.”

Swaminathan later clarified in a tweet that people shouldn’t make those decisions outside of public health regulations.

“Data from mix and match studies of different vaccines are awaited – immunogenicity and safety both need to be evaluated,” she wrote.

University of Toronto biomedical engineer professor Dr. Omar Khan told 680 NEWS, while the WHO said little evidence on mixing exists, the body is likely only looking at data from clinical trials, which are done by manufacturers that test their individual vaccine.

“When a manufacturer builds a vaccine and they go through to clinical trials, they don’t ever look at mixing and matching. So all the health and safety data is based on their product only,” said Khan.

“[The] same thing for the WHO, just like a regulatory body, it looks at all the health and safety data that comes from a clinical trial and these aren’t mixed.”

Ontario’s Chief Medical Officer of Health says it’s possible that Swaminathan’s comments were misinterpreted, urging people not to turn away the second shot of Pfizer or Moderna as they’re both “the same vaccine.”

Canada’s top health officials and the Prime Minister have long recommended mixing vaccines, particularly Moderna and Pfizer – two mRNA treatments readily available to provinces as the country’s vaccination rate soars.

“Looking at data, looking at how to protect Canadians best, we have taken some strong decisions that quite frankly, are bearing out,” Justin Trudeau said on Tuesday.

“We’re seeing record numbers of uptake of vaccinations, we’re seeing a serious and sustained decline in cases.”

As of Monday, more than 50 per cent of eligible Canadians – at least 12 years old and up – have had their second shot.

Ontario’s top doctor, meanwhile, once again repeated his call that even the youngest of residents get vaccinated as soon as possible.

Moore says there remains a lack of uptake among younger crowds aged 12 to 17, saying that teenagers must be fully protected if schools are to return to in-person learning in September.

Moore also says that while indicators remain promising in the province, he “absolutely expects a rise in COVID activity in September,” but wouldn’t go as far as to predict a fourth wave.

“…Especially around the third week of September in congregate settings,” Moore said.

Ontario is set to move into Step 3 of its reopening plan on Friday, which will allow for indoor dining, among the easing of other restrictions.

Moore says everyone must remain vigilant and cautious, adding that masks indoors must be worn at all times with mask-wearing outdoors in large groups also suggested.

As of Tuesday, just over 10.1-million Ontarians have at least one dose or 69.0 per cent of the total population, and 79.4 per cent of adults 18-plus.

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