A new variant of COVID-19 ‘Mu’ has been detected in Ontario. How concerned should we be about reports that it might be vaccine resistant?

Even as the Delta variant remains the dominant strain of COVID-19 globally, scientists warn that a new variant called ‘Mu’, already detected in Ontario, contains a set of mutations that indicate it could be resistant to neutralizing antibodies. derived from vaccination. and infection.

The good news is that the number of global Mu cases, or B.1.621 as it is officially called, is small compared to those in the highly communicable Delta and has even declined in some regions in recent months.

But the bad news is that since Mu was first detected in Colombia in January, the variant has spread to about 42 countries, including 49 US states.In Miami, Florida alone, Mu is responsible for roughly 10 percent of all COVID patients, behind Delta.

In Ontario, the variant was first detected on June 23 and has since been found 168 times in the province, mostly in the GTA.

“Any viral variant that is starting to spread is definitely something to keep an eye on, especially when we don’t yet know how immune-elusive it is,” said Stephanie DeWitte-Orr, a virologist and professor of health sciences and biology at Wilfrid Laurier University.

“Right now, Mu is a variant of interest, which means that the mutations it has qualify to be something we should look at. The mutations look like something that could be a more transmissible virus or it could be a more immunoevasive virus or a combination of that. “

On August 30, the World Health Organization (WHO) added Mu to its list of variants of interest, which includes four other strains, such as Lambda, first discovered in Peru last December and which has since spread to 29 countries.

The WHO defines variants of interest as those strains with genetic changes that are predicted or known to affect things like transmissibility, disease severity, and immune escape, and that have caused significant community transmission in several countries with increasing prevalence. .

Variants of interest are different from more serious variants of concern, which are characterized by increased transmissibility and virulence, such as Delta and earlier Alpha, which drove Ontario’s third wave.

WHO experts continue to emphasize that Delta, which has become the dominant strain of the coronavirus worldwide, remains a major concern due to the fact that it is up to 60% more transmissible than the previously dominant Alpha and its ability to outperform other variants. And they point out that, so far, Mu hasn’t been able to pass on to the extent that Delta has, even if her genetic makeup suggests she might be better at evading immunity.

“In a sense, these viruses compete with each other, not just us,” said Dr. Mike Ryan, executive director of the WHO health emergencies program. during a press conference on Tuesday. “Any virus that emerges has to be able to compete with the ‘best in class’ and right now the best in class in terms of transmission is the Delta variant.

“The Mu variant contains genotypic sequences and structures that would indicate that it might be better at escaping the vaccine or other things, but that won’t matter if it can’t be transmitted efficiently.”

Mutations are essentially random errors that are created when a virus makes copies of itself. Many mutations are known as “loss of function” mutations that result in the virus becoming less effective or productive or even dying. But occasionally “gain-of-function” mutations will occur that make the virus more resistant, virulent, and transmissible.

“This is how viruses work,” DeWitte-Orr explained. “Loss-of-function mutations disappear and gain-of-function mutations are going to beat anything before.”

In its weekly epidemiological update On August 31, WHO noted that the global prevalence of Mu among sequenced cases is currently below 0.1%, “the prevalence in Colombia (39%) and Ecuador (13%) has steadily increased.”

The agency said more studies are needed to understand Mu’s characteristics and will continue to monitor the variant’s trajectory in South America, as well as how Mu interacts with Delta.

In Canada, 196 cases of Mu have been detected nationwide to date, according to the Public Health Agency of Canada, with the vast majority in Ontario. The agency says the majority were from July and that over the past few weeks, “B.1.621 lineage cases have decreased in Canada.”

Public Health Ontario reports that as of August 14, the majority of Mu cases had been detected in Peel (29), York (24), Toronto (20), Hamilton (15), and Halton (10).

As of now, “there is certainly no cause for alarm,” said Arinjay Banerjee, a virologist at the University of Saskatchewan who has been studying coronaviruses for eight years. He noted that while some emerging research suggests that the Mu variant is more resistant to being neutralized by antibodies, in general, the antibodies still work.

“The data shows that if you are vaccinated, you will be protected,” Banerjee said. “If the virus is less neutralized, that does not mean that vaccinated people are seriously ill with COVID-19.”

TO pre-print study released earlier this week A team of Japanese researchers found that the Mu variant is “highly resistant” to blood serum collected from vaccinated individuals and people who had recovered from COVID-19. The study, which has not yet been peer-reviewed, also found that Mu was “significantly more resistant” to serum from people who had recovered from COVID-19 than Beta (B.1.351), which until now was thought to be the most resistant variant.

“Given that breakthrough infection by emerging variants is a major concern during the current COVID-19 pandemic, we believe our findings are of great public health interest,” the authors note.

Mu hasn’t gone unnoticed by vaccine manufacturers either. In an email to the Star, Christina Antoniou, Pfizer Canada’s director of corporate affairs, said the company is currently evaluating the effectiveness of the COVID Mu vaccine in a laboratory study and hopes to share its findings soon.

He said that Pfizer and BioNTech are confident in the protection and safety of the two-dose vaccine, which “remains very effective in preventing COVID-19, including variants, and to date, no variant, including Delta, appears to have escaped the protection of the vaccine “.

Simply put, it’s still early days for the Mu variant and we don’t know yet if it has Delta’s staying power, says DeWitte-Orr.

“Some variants will emerge and they will not take hold. It’s a numbers game, ”he said. “The Mu variant has sequence changes that make it look like it could be a problem. It’s different enough that you have to see it. “


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