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Dr. Nita Patel returns a box of potential coronavirus vaccines to a fridge at Novavax labs in Rockville, Md., on March 20, 2020.ANDREW CABALLERO-REYNOLDS/AFP/Getty Images

In recent weeks, medical tests that can establish whether someone is actively infected with the new coronavirus have been a crucial tool for helping identify who needs to be treated, who needs to self-quarantine and where clusters of COVID-19 are breaking out in the general population.

But with many countries, including Canada, shifting to a new mode of existence that strives to reduce proximity and personal contact, a different kind of testing is needed that could be essential to keeping health facilities and society functioning while the pandemic runs its course.

This kind of testing, broadly known as “serology” because it requires a small sample of a patient’s blood serum, cannot only detect individuals who are in the throes of fighting the virus but also those who have already been exposed and who have managed to clear it from their systems. Based on how other viruses behave, they are presumably immune from COVID-19, likely for months and potentially for years.

“In time, that will tell us how many people have to be vaccinated and what the probability of an outbreak is,” said David Kelvin, an immunologist at Dalhousie University in Halifax, who received federal funding this month to develop portable testing for COVID-19.

Tests that are in high demand to identify active infections are based on a laboratory method known as PCR, which can detect the presence of genetic material from the virus in a nasal or throat swab.

The advantage of serology is that it is cheaper to mass produce and does not require the virus to be present. Instead, it detects antibodies, the tiny, Y-shaped molecules that our immune systems generate to intercept infectious agents.

Globally, several labs are working on serology tests that can screen for COVID-19-specific antibodies. Biomerica Inc., a California-based biomedical company, announced last Tuesday that it has begun shipping initial samples of a serology test it has developed to health officials in multiple countries. Such tests are not yet widely available.

In Canada, Charlottetown-based AffinityImmuno Inc. is aiming to scale up production of a test that it hopes to start distributing in the next few months.

Company president Jonathan Zuccolo said he realized last month that he was well set up to do precisely the kind of work needed to develop a COVID-19 antibody test. He began with viral proteins that were shipped from a source in China. The proteins were not from the virus itself, but rather were synthesized to mimic those that protrude from the virus’s outer envelope based on the genome of COVID-19.

Next, he injected those proteins into two chickens and waited. Last week, after the hens laid eggs, he was able to crack some open and detect the antibodies that the chickens had naturally created.

The antibodies can be used to validate a blood test that can determine, within a matter of minutes, if someone has been exposed to COVID-19. While it would not have the confidence level of a PCR test for an active infection, it could potentially serve as a first round of screening to help determine whether someone should be prioritized for further testing.

Additionally, Dr. Zuccolo said his company is working to develop a test that would show who in the population had previously come down with the virus and can safely interact with others.

“The immediate need is to see who is sick right now,” he said. “But if you start looking across the population, I think you’ll find that there are people who have the COVID-19 antibodies who have never experienced any significant symptoms.”

At the moment, the number of people who fall into this category is unknown but probably still too low to justify whole-population testing for COVID-19, even if this were feasible across Canada. However, an antibody test would greatly aid epidemiologists tracking the spread of the virus and hospitals who need to know who can be cleared to work directly with infected patients.

Last Wednesday, researchers at the Icahn School of Medicine at Mt. Sinai Hospital in New York released their protocol for a COVID-19 antibody test that they developed based on viral proteins that they were able to synthesize on their own. To determine if the test works, they used it on blood samples from patients who have recovered from COVID-19.

Fatima Amanat, a doctoral student who was the lead author on the work, said in the near term the test could be used to identify potential donors for a procedure known as convalescent therapy. The procedure involves people who have already been infected and are virus-free providing serum with antibodies to those whose immune systems are unable to respond quickly enough to fight off COVID-19.

“The serum could be administered to a patient who could be dying,” she said.

Maxim Berezovski, a University of Ottawa biochemist, is working on a system that could eventually allow people to test themselves for antibodies at home and could be applied to a range of viruses. Given the upheaval caused by COVID-19, the ability to rapidly scale up such a technology would be an important tool for avoiding a repeat of the current pandemic.

“This is our future,” Dr. Berezovski said. “We could eventually be doing many diagnostic tests at home and then more detailed tests at clinics.”