Vaxx Populi: In 2020-21, Canada saw only 69 confirmed cases of influenza. Some experts worry that we may have lower immunity to the flu, after nearly two years of social distancing.
Email from FluWatchers arrives in my inbox every Tuesday morning, asking me to click on a Health Canada website to answer two questions: Have I had 1) a fever or 2) a cough in the last week? The whole process takes five seconds. I am one of tens of thousands of volunteers across the country who respond to that short weekly survey (depending on responses, there may be a few more inquiries), a key but low-tech part of the national influenza surveillance system.
For those who ignore the flu as nothing more than a bad cold, consider this Statistics Canada data: Between 2015 and 2019, on average, “influenza and pneumonia” was the sixth leading cause of death in the country, killing approximately 7,333 Canadians annually. Like COVID, it hits the most vulnerable hardest, but it is also capricious, hitting the young and healthy as well.
Every flu season begins with uncertainty. As the vaccine is reformulated annually, depending on the flu strains expected to dominate, it can take months of real-world data before experts can determine its effectiveness. In 2019-20, the latest year for which there are large amounts of data, the flu vaccine offered “moderate protection against influenza A (H1N1), at 43%, and good protection against influenza A (H3N2) and influenza B, at 50 percent and 65 percent, respectively ” Health Canada reported.
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The 2019-20 season ended “abruptly”, eight weeks earlier than normal, at the end of March 2020, Health Canada reported. the because it was the closure of schools and businesses, as well as of people who stayed home at the beginning of the pandemic. “All our measures against influenza squashed COVID,” says Dr. Jeff Kwong, Professor of Family Medicine and Public Health at the University of Toronto
The 2020-21 season was even more unusual due to “very low flu circulation” Health Canada reported. At the end of the flu year, only 69 cases of flu had been confirmed in laboratories, a sharp decline from “the last six seasons in which an average of 52,169 flu detections were reported.”
There is concern that the coming Cold and flu season can be more “normal.” Vaccines mean that people are mixing in ways that were unthinkable a year ago. Schools are back in operation and, in many provinces, the indoor cafeteria is returning to full capacity. And that means people have a much greater chance of catching viruses, including the flu.
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“As COVID-19 containment measures relax around the world, cases of other respiratory viruses whose activity was suppressed by COVID-19 measures in 2020-21 have begun to resurface,” noted the authors of a prepress studio which modeled what flu season might look like in the United States for the Centers for Disease Control and Prevention (CDC). They point to Western Australia, which found that respiratory syncytial virus (RSV) cases among children were much higher than previous seasonal peaks after the nation relaxed its social distancing measures. And the number of RSV cases began to rise in the United States this summer, much earlier than usual, according to the study. In addition, Hong Kong has reported seven times the number of large school outbreaks of acute upper respiratory infections this year.
In Canada, doctors are already treating more patients with colds and respiratory viruses. The return of common rhinoviruses and RSV worries Kwong. “If they are spreading, why not the flu?” he says. In particular, it points to the number of RSV cases in Quebec and, more recently, in Ottawa. The virus, which primarily affects children, is second only to influenza to cause serious illness, he says.
In the United States, there are growing concern that nearly two years of pandemic precautions mean that our immune system has not caught up with new viruses and is operating with increasingly out-of-date information, much like smartphones before operating system updates. In a typical flu season, there are about 500,000 hospitalizations in the United States, according to the CDC’s preliminary study. Their model suggests that there could be 100,000 “additional hospitalizations in 2021-22” in “a major compensatory flu season in 2021-22 due to a light season in 2020-21.”
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“I’m not so convinced of that,” says Kwong, regarding the study’s model. On the one hand, it points out that immunity can last for a long time. For example, he says, when the H1N1 pandemic struck in 2009, older Canadians were less affected than expected, probably because they had been exposed to a similar version from the flu years before. “If you can have some immunity from decades ago, then not having the flu for a few years may not make a big difference,” he says.
“Control the things you can control” is Kwong’s simple advice. “We’ve learned so much from COVID,” he says, that we just need to “use some of those tools to prevent flu,” including flu vaccination and other basic public health measures that have become standard during this pandemic: washing your hands. hands, wear masks and minimize social contacts. Improving ventilation will also be helpful, including through HEPA filters like those used in schools.
Canada is also preparing. On October 7, the National Immunization Advisory Committee (NACI) reported that all seasonal influenza vaccines “may be administered at the same time or at any time before or after the administration of other vaccines, including COVID-19 vaccines.” . The provinces and their local health units are already increasing vaccination campaigns against influenza for the most vulnerable, such as older people and those in congregated settings such as long-term care homes. In Ontario, flu shots for the general population under 65 will be available from November 1.
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As in previous years, the flu season may not be as bad as expected. Current surveillance updates in Australia, which has a previous seasonal flu season, reports that “community flu-like disease activity remains at historically low levels in 2021,” although that may be partly due to recent strict closures in the country.
While no one is sure how Canada will fare this winter, everyone agrees on one thing: After nearly two years of COVID-19, with a healthcare system on edge, making sure as many people as possible get away. get a flu shot. more important than ever.