National Post (National Edition)
Antibody Testing: Canada’s Secret Weapon against COVID-19
Why we need to be thinking ahead in our COVID defences
Testing for active cases of COVID-19 is nothing new. We’ve all relied on prevalence reports to assess our overall risk since the pandemic began, over 6 months ago. But, while the PCR (polymerase chain reaction) test is extremely useful in identifying cases of acute infection and is the most widely used COVID-19 test, it has its limitations.
If you suspect you have COVID-19, the PCR test can only detect a viral infection for a very narrow window of time; up to 21 days following exposure or when symptoms appear. And, to make matters more complicated, it’s possible to be asymptomatic during that time. This means that if you don’t experience any symptoms until after the virus has stopped actively replicating, a PCR test will not detect COVID-19 and you’ll never know you had the infection.
This is where antibody testing – blood tests that tell you if you had COVID-19 in the past – becomes very useful.
Antibodies are a type of blood protein that your body immune cells make in response to a foreign substance in your blood, such as a virus. You can think of antibody production as an in-built defence mechanism. Blood tests can detect COVID-19 antibodies with enormous accuracy and are becoming available throughout Canada to confirm previous exposure to the virus.
As a general rule, antibodies have the potential to offer protection against specific viral strains. In other words, if you’ve already had a virus and produced antibodies against it, you typically can’t be infected by it again.
We don’t know yet whether having antibodies against COVID-19 can protect you from contracting this particular disease again in the future. However, we do know that 90 to 95% of people who’ve been infected with COVID-19 produce antibodies 14-21 days after they show symptoms. And, scientists may well obtain evidence in the coming months that the presence of COVID-19 antibodies is protective against the disease.
What does this mean for the Canadian population?
The Canadian Agency for Drugs and Technologies in Health states: “There are times when PCR-based testing and serological testing may be used in complementary ways”.
It can be really helpful for researchers to cross-reference results from PCR and antibody tests in order to understand a virus better. So, if more Canadians are tested for COVID-19 using both methods – PCR whilst they’re symptomatic and antibodies a few weeks or months later – they’ll help gather data that could end up being extremely helpful for scientists at a later date.
What if, a few months from now, we have proof that everyone who has produced antibodies against COVID-19 can’t be re-infected? If Canada was ready with PCR and antibody test data to analyze, we could make stronger, faster policy decisions around:
• Returning to work
• How we use personal protective equipment
• Loosening of social distancing practices
More proactive, complementary testing practices could help Canada prevent a second wave of COVID-19 by: 1) understanding how humans respond to the virus, and 2) identifying higher risk population groups. For example, with large data groups, we may notice more COVID-19 cases in certain neighbourhoods, workplaces, or points of contact.
We also have yet to enter flu season, during which many people will undoubtedly worry that their symptoms are reflective of COVID-19. If we’ve been collecting data through PCR and antibody testing over the summer, then it transpires that antibodies offer protection against COVID-19, everyone who develops flu-like symptoms who’s already had COVID-19 may not need to worry about contracting it again. In this way, antibody testing could help people have a more positive mindset about their health over winter.
What can you do to help?
If you’re currently experiencing COVID-19 symptoms, have a PCR test as soon as possible. If it’s been several weeks or months since you had symptoms, or you’ve been exposed but haven’t had symptoms, consider an antibody test.
Health Canada has very high standards when it comes to approving COVID antibody tests and, although there are slight variations between tests, all are equally valid. It’s anticipated that antibody testing will become more accessible in time, as more evidence is gathered to support its benefits. Follow your provincial guidelines to see what’s available to you and do your part in keeping Canada ahead of the game with our strategic data collection.
THERE ARE TIMES WHEN PCR-BASED TESTING AND SEROLOGICAL TESTING MAY BE USED IN COMPLEMENTARY WAYS