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explainer

A woman wearing a protective mask takes a stroll in a park in Montreal, on July 6, 2020.Paul Chiasson/The Canadian Press

The summer wave is upon us. In several parts of the country, COVID-19 cases and waste-water levels are increasing again in a new surge driven by the highly contagious Omicron subvariants BA.4 and BA.5. For Canadians who have been living with the reality of the pandemic for more than two years, it’s no longer a matter of asking about masks and vaccines. Here’s what Canadians need to know about the new subvariants, getting boosters and the likelihood of reinfection.

What do we know about the Omicron subvariants BA.4 and BA.5?

The Omicron subvariants BA.4 and BA.5, which were first identified in South Africa in January and February, 2022, are driving a surge of cases in many provinces. BA.5 is poised to become the dominant variant strain.

The good news is that BA.4 and BA.5 do not appear to cause more severe disease than previous versions of Omicron. “We are not seeing BA.4 and BA.5 being more virulent or more pathogenic compared to the previous subvariants BA.1 and BA.2,” said Dr. Nazeem Muhajarine, professor of community health and epidemiology at the University of Saskatchewan.

However, he noted that because BA.4 and BA.5 are highly transmissible, the sheer number of cases could still lead to a greater strain on our health care system. Dr. Muhajarine pointed to the United Kingdom and France, where the BA.5-driven wave is leading to an uptick in hospitalizations. “We see what is happening in Europe and that is repeated in Canada three to four weeks later. That’s been the pattern all throughout the pandemic,” Dr. Muhajarine said.

What are the symptoms of BA.4 and BA.5?

The symptoms of BA.4 and BA.5 are similar to the original Omicron variant, which are distinct from previous versions of COVID-19, said Raywat Deonandan, epidemiologist and University of Ottawa associate professor.

Omicron symptoms include fever, runny nose, coughing, sore throat, aches, muscle pain and fatigue. Gastrointestinal symptoms and the loss of smell and taste are not as prevalent as in previous variants.

“The most dominant are the coldlike symptoms, which is unfortunate because you can’t tell the difference between a cold and COVID-19,” said Deonandan. “But there’s so much COVID now, you can assume that if you have a cold, it’s probably COVID.”

How often can you be reinfected with Omicron?

BA.4 and BA.5 are both particularly adept at evading vaccine-induced immunity and immunity acquired from previous COVID-19 infections. A U.K. study published in the journal Science found that antibodies from BA.2 are less effective at neutralizing the BA.4 and BA.5 subvariants, leading to more reinfections. “So in other words, if you were infected with an earlier Omicron subvariant, that is not going to protect you from being infected again from BA.4 and BA.5,” said Dr. Muhajarine.

Research led by University of Toronto researcher Igor Stagljar found immune protection acquired by a vaccine or a prior infection lasts only four months against BA.4 and BA.5.

“If someone had COVID at the beginning of this year or if someone got vaccinated at the beginning of this year, this means that we have zero – almost zero – protection in the form of neutralizing antibodies,” against the new variants by the summer, said Dr. Stagljar.

There are also multiple factors at play that can affect immunity, including age and pre-existing medical conditions, that could make someone more vulnerable to reinfection, said Dr. Muhajarine.

How effective are current vaccines against Omicron?

Our current vaccines were tailored solely to the original virus. These vaccines are no longer effective at preventing infection against BA.4 and BA.5, said Dr. Mahajarine. However, he notes they still offer a great amount of protection against severe disease and hospitalization.

Vaccine manufacturers Pfizer and Moderna are working on new bivalent boosters that target specific mutations in the spike protein found in both the old strain and newer Omicron strain.

Though this tweaked formula isn’t expected to land until the fall, experts say it shouldn’t be considered outdated. “If we have, in this vaccine, representation from very different strains, or different variants, then we can assume that we get broad protection also against future variants,” said Dr. Volker Gerdts, director and CEO of the Vaccine and Infectious Disease Organization.

If I’ve already been infected with COVID-19, do I need to get a booster?

Yes, the National Advisory Committee of Immunization (NACI) strongly recommends a booster dose for all adults, and for adolescents who are considered to be at high risk for severe disease. Studies have also found that people who were not vaccinated and had been previously infected with BA.1 were more likely to get reinfected with BA.4 and BA.5 compared with those who had been vaccinated. “The implication being that getting Omicron, over, say, getting vaccinated, is not a smart way to build immunity against being reinfected with Omicron or another variant,” said Dr. Muhajarine.

My age group is now eligible for a second booster. Should I get it right away?

Amid the growing Omicron wave, provinces and territories across Canada have been expanding eligibility for fourth doses. For example, in Ontario, everyone between 18 and 59 years old who received their last dose more than five months ago – and is at least three months past their last infection – is now eligible for a second booster.

Ontarians who receive a second booster dose will still be eligible in the fall for new bivalent vaccines that specifically target Omicron.

Quebec, New Brunswick, Prince Edward Island, Yukon and Nunavut have also expanded eligibility for fourth doses to all adults.

When deciding when to get your fourth dose, Deonandan had simple advice for those who are eligible: “Get it now. Don’t hesitate. We spend so much time trying to calculate the optimal time to maximize our protection – that’s a fool’s game because the virus is all around us.”

Dr. Muhajarine said to also evaluate your personal risk of exposure and the need for protection. For instance, if you’re planning to travel internationally to a country with high COVID-19 rates, you may consider getting your booster two to three weeks before you leave. Other personal circumstances, like attending a wedding or returning to work, could also impact the timing of your booster.

Moreover, many health experts now say that having two vaccine doses should no longer be considered fully vaccinated. Instead, it should be considered a three-dose vaccine.

How soon after a COVID-19 infection should I get a booster?

NACI recommends that anyone who gets infected with COVID-19 should wait three months before getting a booster dose. A longer interval between infection and vaccination “may result in a better immune response as this allows time for this response to mature in breadth and strength, for circulating antibodies to decrease, thus avoiding immune interference when the vaccine is administered.”

How effective are masks against BA.4 and BA.5 in indoor settings?

“High-filtration masks are very good at reducing both inhaling the tiny viruses through your mouth and nose, and if you have the virus inside your body, from expelling it into the air,” said Dr. Muhajarine. Since COVID-19 is transmitted by air, a quality mask – such as an N95 or KN95 – is one of the most effective and cheapest ways to cut down transmission, whether it’s BA.4 or BA.5, or any other variant, he said.

Although most mask mandates have been dropped across the country, many health experts recommend wearing a mask on public transit, and in grocery stores or other crowded indoor spaces. Some health professionals are even calling for indoor-mask wearing requirements to be brought back.

“We need to stick to our masks for a little bit longer because they really do protect us and others around us,” Dr. Muhajarine said.

Rapid tests can still detect BA.4 and BA.5, but using them comes with caveats.Jeff McIntosh/The Canadian Press

Are rapid tests still accurate with Omicron?

Yes, rapid tests can still detect BA.4 and BA.5, but using them comes with caveats. Unlike PCR tests, which amplify small amounts of genetic material to confirm the presence of the SARS-CoV-2 virus, rapid tests detect the presence of proteins – or antigens – found on the surface of the virus. A fairly high concentration of the virus is needed to produce a positive result with the rapid test.

If you have symptoms and test negative on a rapid test, that does not necessarily mean you are in the clear, said Deonandan. “If you’ve been vaccinated and you become infected with Omicron, you’re going to get your symptoms before you get a viral load. That’s your vaccine doing its job – it’s producing all this phlegm and mucus to prepare your body to fight off this infection that’s coming,” he said. Deonandan recommends repeated testing over a few days. “If you test negative, you still might be having a burgeoning infection.”

However if you test positive on a rapid test, Deonandan said that you can trust that it is likely accurate.

What treatments are currently available for COVID-19?

Health Canada has approved a handful of treatments for COVID-19, including drugs that reduce or stop the virus from multiplying in human cells and drugs that treat the symptoms of COVID-19.

Pfizer’s Paxlovid is an oral antiviral drug that is authorized to treat symptomatic adults with mild to moderate COVID-19 and are at high risk of serious illness.

Evusheld, which is developed by AstraZeneca, is designed to protect people with compromised immune systems, including transplant patients. Prospective patients must be unlikely to mount an adequate immune response to COVID-19 vaccines, or be among the few for whom vaccination is not recommended. Unlike Paxlovid, Evusheld is only approved for people who are not infected with COVID-19.

But some medications approved by Health Canada are no longer effective with the arrival of new variants, said James Heilman, an emergency physician in Cranbrook, B.C. For example, several months ago, he was using sotrovimab, an injectable antibody, to treat patients with severe COVID-19, but with the onset of Omicron, the treatment no longer works.

With files from Wency Leung, Carrie Tait, Dustin Cook and Canadian Press

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