COVID at the highest levels
Posted on Wednesday, September 9, 2020
By Jessica Sinclair
What’s the deal with reinfection? When will we see a vaccine? How does age play into it? The answers to these questions seem in constant flux, which is why Health Canada hosted a Science Town Hall on August 28th to get the latest on our country’s rapid-response research. University of Ottawa Faculty of Medicine professors Mona Nemer and Marc-André Langlois shared the virtual stage with Chief Public Health Officer Theresa Tam, Minister of Health Patty Hajdu, and other key players in Canada’s efforts against the current COVID pandemic.
Some key takeaways from the 90-minute session:
How are the science and policy worlds coordinating on COVID?
“There has never been a better demonstration of the importance of science for policy than in managing this pandemic: from the public health measures of masks to whether we send children back to school or not,” said Dr. Mona Nemer, professor in the Department of Biochemistry, Microbiology and Immunology, and Canada’s Chief Science Advisor.
It’s critical to understand who is at risk, how long the infection lasts, and how people transmit the disease, she said, because these all have profound implications for policy.
What does reinfection really mean?
According to Dr. Langlois, Canada Research Chair in Molecular Virology and Intrinsic Immunity at the uOttawa Faculty of Medicine, there has been some confusion in the coverage of reinfection. The key point to note is that reinfection is not the same as coming down with COVID-19 twice.
“The virus is enveloped by a membrane it has stolen from infected cells,” said Dr. Langlois. “This acts as a camouflage and the immune system really struggles to find it.”
Upon first being infected, the naïve immune system puts up its indiscriminate first line of defense for about a week before coronavirus-specific antibodies start to emerge. Later on, if you are exposed to the virus again, the antibodies kick in right away, binding to the virus and trying to prevent it from entering the airway cells.
It is possible to get reinfected with SARS-COV2—that is, to have the virus successfully enter your airway cells even if you have already had COVID-19—but what is not expected is to get the COVID-19 disease twice. The antibodies that are present are busy tagging infected cells to be cleared away.
How are the vaccine prospects coming along?
Vaccine development is proceeding faster than normal, because many of the process that are often conducted sequentially are in this case completed either in parallel or with substantial overlaps. After 28 days of safety data, trials can often begin their next phase while continuing to track safety. Dr. Teresa Tam noted that 60 percent of Canadians now say they will accept the vaccine, and that this proportion is a decrease from prior survey results.
“What seems to make Canadians hesitate is the fast pace of vaccine development,” said Dr. Tam. “It is giving them pause about safety, and a lot of people are planning to take a wait-and-see approach.”
Indeed, Dr. Tam herself indicated that research doesn’t stop once a vaccine is approved by a regulator for widespread use. The preliminary data show that among vaccines being developed, people who receive them are showing about four times the antibody levels compared with someone who has actually experienced a COVID illness.
How accurate are the tests we receive at the testing centres?
Dr. Mel Krajden, Medical Director of British Columbia’s Public Health Laboratory explained that the mainstay for diagnosing COVID-19 is nucleic acid-based testing, which detects the RNA from the virus and is thought to be 90-95% sensitive and specific to the virus 99.5% of the time. About 1 in 200 people will have a false positive test, often from technical errors. Throat swabs are a little less sensitive than nasal-pharyngeal swabs. Saline gargles and saliva testing are also on the rise.
“One of the most important factors in testing is the turnaround time,” said Dr. Krajden. “It’s crucial that we inform people of their infection status before they have to make key decisions about where to go and who to see.”
What makes some people susceptible to the illness and others asymptomatic?
Dr. Cate Hankins, professor in the Department of Epidemiology, Biostatistics and Occupational Health at McGill, says there are a number of protective factors that are being floated for the disease. Given that many of the seasonal common colds in circulation are coronaviruses, it stands to reason that having been exposed to those recently may offer some partial immunity against the spike proteins that SARS-CoV2 uses to break into cells.
Children also have a number of advantages, including a generally robust immune response.
“Childhood vaccinations, particularly for polio, look like they are associated with more asymptomatic cases than symptomatic,” said Dr. Hankins.
The famous spike proteins that give the virus its distinctive shape attach themselves to the lung and airway cells on a receptor called ACE-2—a receptor that helps us control our blood pressure. If you have fewer of them, you may be less likely to develop symptomatic COVID.
As for masks, not only do they contribute to slowing the spread of COVID, Dr. Hankins said that if you contract the new coronavirus while wearing a mask you are more likely to have an asymptomatic case, which suggests that dose is important. Some of the data to support this came from natural experiments on cruise ships that did and did not implement mask use.
When it comes to sex differences, Canada is in atypical in its ratios. Worldwide, 60% of the deaths are among men, but 53% of our own deaths are among women. This is partly because our long-term care facilities were so hard-hit compared with wider community cases, but on average women do mount a more robust immune response to infection.