Updated: June 26, 2020

When will a blood test be widely available to look for evidence of prior virus exposure?


Serology testing for SARS-CoV-2 is a blood-based test that can be used to identify whether a person has had prior exposure to the virus by looking for COVID-19 antibodies [1,5]. According to the Canadian Agency for Drugs and Technologies in Health, the performance and role of serology tests in clinical settings have not been completely demonstrated and evidence is lacking to confirm that individuals are protected from reinfection of COVID-19 [2]. On May 12, 2020, Health Canada authorized the first COVID-19 serological test for use in Canada [3]. Currently, the COVID-19 Immunity Task force, based at McGill University’s School of Population and Global Health, is collecting blood samples from large groups of individuals, which include asymptomatic or mildly symptomatic people to provide the data needed to understand the scale of infection in Canada [4]. They are also currently conducting targeted population serological testing, which helps shed light on the immunity status of vulnerable populations [4]. In the next two years, Canada’s COVID-19 Immunity Task Force is hoping to collect and test at least one million Canadian blood samples to track the viral exposure in the general population and in specific groups at greater risk of having been infected (i.e., health care workers, indigenous communities, and residents of long-term care homes) [3].  
According to the US Federal Food and Drug Administration (FDA), the performance of serological tests is analyzed by their sensitivity and specificity [5]. The sensitivity of a test describes its ability to successfully identify individuals who have SARS-CoV-2 antibodies (true positive rate), while the specificity of the test describes its ability to identify individuals without SARS-CoV-2 antibodies (true negative rate) [5]. The sensitivity of tests, approved by the FDA, currently range from 90-100% and the specificity range from 96-100%, indicating the possibility of an inaccurate result [5]. The complete list of serological tests and their effectiveness is available here. In Canada, once priority groups have been tested, serological tests may be used to stimulate sectors of the economy that are contingent on the gathering of people [2]


The development of a detailed, robust answer relies on several factors. To provide a detailed REAL Note requires knowing the following:
o   Ontario and/or Canadian decision making and policy implementation 
o   Research funding allocated towards serological testing in Ontario and/or Canada 
o  Availability of testing and laboratory equipment, trained staff, and proper facilities


Review of Evidence

Resource Type/Source of Evidence Last Updated
Serology-based test for COVID-19
— John Hopkins Bloomberg School of Public Health: Center for Health Security
Report Last Updated: June 15, 2020
Serological Tests for COVID-19
— Canadian Agency for Drugs and Technologies in Health
Horizon Scan Last Updated: May 27, 2020
Statement from Health Canada on COVID-19 Serological Tests
— Government of Canada
Statement Last Updated: May 11, 2020
— COVID-19 Immunity Task Force
Background Information Last Updated: June 25, 2020
EUA Authorized Serology Test Performance
— U.S. Food & Drug Administration
Report Last Updated: June 17, 2020
Disclaimer: The summaries provided are distillations of reviews that have synthesized many individual studies. As such, summarized information may not always be applicable to every context. Each piece of evidence is hyperlinked to the original source.

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