There are many unknowns about how a new wave of COVID-19 will play out in Canada in the coming weeks, but clinicians and scientists say many of the lessons learned from previous ones can help mitigate its impact. Although the virus continues to change, some of the basic public health advice still applies, said Jeff Kwong, a professor of family medicine and public health at the University of Toronto. “Ventilation, masks and vaccines still work to varying degrees and for different things,” Dr Kwong said. In several parts of the country, COVID-19 cases and sewage levels are rising again, raising concerns that another wave is already underway. Data from the Ontario COVID-19 Scientific Advisory Panel show that several indicators in that province, including positive tests, sewage levels and hospitalizations, suggest the virus is increasing. The number of cases in Quebec is increasing. And according to federal wastewater surveillance data, last updated on July 5, six of 22 recorded locations across the country showed a possible increase in levels of COVID-19 in their wastewater, compared to the previous seven days. These include locations in Halifax, Charlottetown and Vancouver. “It’s a question of how big and how serious, but it’s definitely a wave,” said Tania Watts, an immunologist at the University of Toronto. One factor that will shape how this wave plays out is the amount of immune protection the public has against the virus. New analysis of blood test data from the Canadian Immunity Task Force on COVID-19, released Wednesday, showed that the percentage of Canadians who had antibodies to SARS-CoV-2 infection, the virus that causes COVID-19 , increased by 45%. This suggests that more than 17 million Canadians were infected by the Omicron variant. Before Omicron was introduced, about 7 percent of the population had infection-acquired antibodies against SARS-CoV-2, the task force said. Meanwhile, nearly 82 percent of the total population is considered fully vaccinated against COVID-19, and nearly 60 percent of those ages 12 and older have received at least one additional dose, according to federal data. However, BA.5, the new variant poised to become mainstream in Canada, can evade immune protection. That means everyone who caught Omicron is now susceptible to re-infection, Dr Watts said. Research led by University of Toronto scientist Igor Stagljar supports this. Using a new antibody test he and his team developed, they found that immune protection gained from a vaccine or previous infection lasts only four months against the new variants, BA.4 and BA.5. “If someone had COVID early this year or if someone was vaccinated early this year, that means we have zero – almost zero – protection in the form of neutralizing antibodies,” said Dr. Stagljar, a professor in the Donnelly Center for Cellular and Biomolecular Research at the Temerty Faculty of Medicine. In addition, some of the drugs used for COVID-19 are no longer effective with the arrival of new variants, said James Heilman, an emergency physician in Cranbrook, BC. For example, several months ago, he was using sotrovimab, an injectable antibody. to treat patients with severe COVID-19, but with the start of Omicron, the treatment no longer works. It’s also now becoming clear that Paxlovid, once considered a potential panacea, is only useful for those at high risk of serious disease, Dr. Heilman said. Despite these new challenges, however, the main way people get infected with COVID-19 has not changed. “Disease has been airborne since the beginning,” said Dr. Heilman, Wikipedia’s medical content editor. This means that high-quality masks still work to reduce the risk of infection, not only from COVID-19 but also from other respiratory viruses, Dr Kwong said. Cloth masks are better than nothing, he said, but emphasized that N95 or KF94 respirators are best. The now-familiar adage that gathering outdoors is safer than indoors still holds true, Dr. Watts said. The same goes for the idea that small groups are safer than large crowds. the chances of catching COVID-19 in a room of 1,000 people remain higher than in a room of 10 people, he said. And although contact with contaminated surfaces may not be the main route of transmission, hand washing is still a good idea, Dr. Watts said. However, some health messages will now have to be modified or cancelled, they said. Keeping two meters away from others won’t necessarily keep people safe, Dr Kwong said. If they spend time in an enclosed space where many people produce a lot of small particles, transmission can occur, even when everyone is at a distance from each other, he said. Current guidelines, which require self-isolation for at least five days after the onset of symptoms or a positive test and coverage when in public from days 6 to 10, could also use revision, Dr. Watts said. In some cases, the virus can be shed after the fifth day, so she recommends doing a rapid antigen test after five days and staying home longer if the test is positive. Dr. Heilman added that people should not assume they are free of COVID-19 just because they test negative on a rapid test. It can take several days of symptoms before people test positive, he said. Additionally, having two doses of vaccine should no longer be considered fully vaccinated, but instead, should be considered a three-dose vaccine, Dr. Watts said. While vaccines don’t fully protect people from infection, they provide good protection against serious illness and reduce the risk of long-term COVID, he said. Given how quickly immunity declines, however, Dr. Stagljar suggested that Canadians can expect to need an additional dose every four to five months. A test that measures neutralizing antibodies, like the one he and his team have developed, could help determine when people need a booster dose, he said. Ultimately, it’s a mistake to think that efforts to stop the spread of COVID-19 can be abandoned just because it’s not killing or seriously illing as many people, Dr. Watts said, adding that infections allow the virus to mutate further. “We all have a societal contribution to make to keep COVID from spreading and worsening the overall pandemic, and also obviously affecting the vulnerable,” he said.
