Many Canadians wonder if the sniffles and sore throat they had in 2020 or 2021 was a simple head cold or COVID-19.
Without a nose or throat swab test done around the time you were sick, the only way you can know for sure if you had COVID-19 is through a special blood test known as a serology test. Serology tests provide evidence of a previous exposure to the virus that causes COVID-19 by testing for the presence of antibodies in blood. They can even detect previous exposures of the virus in people who had COVID-19, but had no symptoms.
Serology tests can also detect previous infections of COVID-19 in vaccinated individuals. If antibodies recognizing several viral proteins are detected, it is an indication of a previous infection. If the individual only has antibodies that recognize the spike protein, the immune response observed is likely the result of vaccination.
Canada’s National Microbiology Laboratory (NML) has been instrumental in advancing serology testing through its involvement in several projects related to COVID-19 serology testing and serosurveillance (examining the immunity of populations).
Here are a few examples of their efforts.
Evaluating Serology Tests
Serological tests play an important role in Canada's overall testing strategy, by assessing the true extent of exposure to COVID-19 in the general population.
“The National Microbiology Laboratory and our partners have assessed a variety of commercial serological tests for detecting antibodies to SARS CoV-2,” says Dr. Michael Drebot, Director of Zoonotic Diseases and Special Pathogens at the NML.
COVID-19 Immunity Task Force (CITF)
The Government of Canada also launched the COVID-19 Immunity Task Force (CITF) in late April 2020 to measure the scope of COVID-19 infection in Canada, understand the nature of immunity following infection and develop improved antibody testing methods.
Dr. Drebot is helping to coordinate the NML’s work within the Task Force.
“The NML has generated a number of serology reference panels. They help ensure that tests perform accurately and reliably in detecting viral antibodies in patient samples,” said Dr. Drebot.
He says large-scale serology testing can give us a better picture of community spread.
“Serology testing can take a snapshot of where we stand in a given moment. It can also shed light on the potential immunity status of vulnerable populations such as Indigenous communities, and residents of nursing homes and long-term care facilities.”
The Task Force has the mission of tracking the spread of the virus in the general population and shedding light on immune responses to SARS-CoV-2 in a diversity of communities, age brackets, populations and occupational groups across Canada.
“Conducting large serological surveys of the Canadian population will measure the scope and scale of COVID-19 infections across the country,” said Dr. Drebot.
Serological surveys of the general population and at-risk subgroups have helped guide important public health decisions during the pandemic, including the distribution of vaccines across Canada.
For example, on November 9, 2020, the COVID-19 Immunity Task Force announced they were mailing out test kits to collect blood samples from households across Canada for the COVID-19 Antibody and Health Survey. The samples were then mailed to the NML for analysis. Participants who were selected for this study were able to learn their results, along with information on what is known about antibody testing.
Learning about long-lasting immunity
In the early days of COVID-19, scientists from the NML developed a variety of their own serological tests, including a specialized test to detect “neutralizing” antibodies. Neutralizing antibodies are able to inactivate virus particles, which means they can usually prevent infection.
“Using these tests, scientists are able to gain important information on possible immunity and long-lasting protection from re-infection of the virus,” said Dr. Heidi Wood, Chief, Rabies, Rickettsia and Related Zoonotic Diseases, Zoonotic Diseases and Special Pathogens at the NML. “These types of tests are also instrumental in evaluating future vaccines to determine their effectiveness before starting clinical trials.”
Developing a laboratory test to detect neutralizing antibodies that are sensitive and specific was a challenge, but NML scientists are experts on developing and running these types of tests.
“We needed all hands on deck when we started studying COVID-19 neutralizing antibodies,” says Dr. Wood, “But we had lots of scientists from the NML volunteering to fill positions. The work is very exciting and can help advance this area of study further throughout the world.”