Why some experts say Quebec’s plan to give different vaccine as 2nd dose is safe and necessary

Jonathan Marchand, a resident of a long-term care home north of Quebec City, got his first dose of a COVID-19 vaccine back in December and he’ll be getting a second dose on Friday. 

But it won’t be from the same company.

“I would have preferred to have received the Moderna vaccine, which was the first dose I received but I’ll take the Pfizer one. It’s almost the same,” said Marchand, a 44-year-old disability rights activist.https://www.dianomi.com/smartads.epl?id=3533

Marchand isn’t the only one who will be getting a vaccine cocktail.

Quebec is rushing to administer second doses to the province’s most vulnerable residents — even if the second dose doesn’t match the first.

Outbreaks at two homes in the Quebec City region have infected more than 50 and killed five even though nearly all residents received their first doses back in December.

A single dose can provide ample protection to most but seniors are particularly susceptible to the disease. And just as it’s time to boost their protection, Moderna deliveries have been significantly delayed by “quality assurance” backlogs.

So health officials are wading into uncharted territory by switching mRNA COVID-19 vaccines while studies on the effectiveness and safety of combining the two are still underway.

On the surface, this may sound like a gamble, but some Quebec experts say it would be riskier to delay the second dose while new mutations of the coronavirus are sweeping through the province.

Vaccine combo could mean stronger immunity: Dr. Horacio Arruda

Some vaccinologists suspect that getting a different type of COVID-19 vaccine for the second dose could stimulate immune cells to tackle variants of concern.

That appears to be the thinking of Quebec’s director of public health, Dr. Horacio Arruda, who said on Thursday that there are stories of people developing even stronger immunity to the novel coronavirus when doses are mixed.

“I think that if you received the Pfizer one, you could receive, probably,  Moderna,” he said.

Protocol is to give the same vaccine, Arruda said, but “if there is no available Pfizer and you have Moderna, I think the recommendation will be that you can change it.”

Studies still need to be done when it comes to mixing in AstraZeneca-Oxford, a viral vector vaccine, Arruda said, but even then people would develop a “good immunity.”

The province’s initial goal was to administer the second dose to residents in CHSLDs around 112 days after the first but, already, about 130 days have elapsed since the vaccine campaign began on Dec. 14. Now Quebec says the goal is to get those residents vaccinated by May 8.

Long-term care homes in Montreal to administer Pfizer

Among those who will likely receive a different second vaccine are long-term care residents in Montreal’s west end.

The CIUSSS du Centre-Sud-de-l’Île-de-Montréal will be giving residents the Pfizer vaccine starting Monday, according to Dr. Sophie Zhang, who oversees 15 long-term care centres.

“We do know that people who are older and have more illness tend to have a weaker response to the first dose,” she said. “Given that, giving them a booster dose would be the best thing to do as quickly as possible.”

Dr. Lisa Barrett, an infectious diseases physician and researcher at Dalhousie University in Halifax, said she doesn’t see any reason to be worried about safety.

Barrett likens the first shot to giving your immune system an elementary school education. The second dose broadens the response to a university level.

“What your first shot does is it sends up a battle cry, if you will, to your immune system to rally those specific troops together to get an immune response that’s good to this particular part of COVID vaccine and then it adds some memory,” Barrett said.

“The quality of the immune response after one shot is generally OK but still not highly sophisticated.”

It’s better to act now rather than wait: epidemiologist

With outbreaks hitting long-term care homes, it’s better to act now rather than wait, said Dr. Gaston De Serres of Quebec’s public health institute (INSPQ).

“If you have a choice of being given the same product or delaying the second dose, then it’s probably better to give the second product than waiting for the Moderna product,” De Serres, an epidemiologist, said.

“Right now, as imperfect as it seems, it’s the most logical approach we can use to protect our most vulnerable.”

Dr. Donald Vinh, an infectious diseases specialist at the McGill University Health Centre who was also a science advisor for the federal COVID-19 therapeutics task force, said it all comes down to a race against the variants. 

Even if the second dose is different from the first, he said, “there is undoubtedly going to be some level of protection that is going to be given or enhanced.”

cbc.ca

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