Back to Top

OHS and CanPath COVID-19 Antibody Study

The OHS is asking a subset of around 12,000 participants who completed the COVID-19 Questionnaire to also provide a small blood spot sample, which will be analyzed to detect antibodies to SARS-CoV-2, the virus that causes COVID-19. If you have been invited to take part, please read these FAQs to learn more about the initiative:

Click to jump to each topic:

About the COVID-19 Antibody Study

What are the OHS and CanPath COVID-19 research initiatives?

  • COVID-19 Questionnaire administered in 2020 across the CanPath cohort of 330,000 participants
  • CIHR and CITF-funded seroprevalence study of 3,000 randomly selected participants
  • CITF-funded seroprevalence study of 20,000 participants in populations at high risk of exposure to COVID-19

Who is conducting the COVID-19 Antibody Study?

The Ontario Health Study is part of the Canadian Partnership for Tomorrow’s Health (CanPath), which has received funding from the COVID-19 Immunity Task Force and the Canadian Institutes of Health Research to collect information related to COVID-19 immunization. All CanPath cohorts are participating in this initiative. This includes the OHS, as well as Atlantic PATH, CARTaGENE (Quebec), the Manitoba Tomorrow Project, Alberta’s Tomorrow Project, and the BC Generations Project.

We are collecting data to share with researchers across Canada and internationally to investigate COVID-19 infection rates in the Canadian population, to understand the science behind COVID-19 immunity, and to study health related outcomes.

CanPath’s COVID-19 Antibody Study is funded by the Government of Canada, through Canada’s COVID-19 Immunity Task Force, and by the Canadian Institutes of Health Research. The Ontario Health Study receives national funding from the Canadian Partnership Against Cancer and regional funding from the Ontario Institute for Cancer Research, Ontario Health (Cancer Care Ontario) and Public Health Ontario. 

When is this study being conducted?

Blood spot sample collection occurred between March and June 2021, and is slated for February through June in 2022. For those selected to partake in the longitudinal study, a second and third blood spot sample will be collected 6 and 12 months after the first sample.

Didn’t I complete a CanPath COVID-19 study in 2020?

Yes. Almost 100,000 CanPath and regional cohort participants completed the CanPath COVID-19 Questionnaire. The information collected by that questionnaire is providing researchers and public health professionals with great insights into how the pandemic has affected the health and well-being of Canadians. This will help them understand how best to respond to the current COVID-19 pandemic as it evolves, and will also inform future pandemic responses.

In 2021 and 2022, CanPath and its regional cohorts are conducting a COVID-19 serology study to see which Canadians have developed antibodies to the SARS-CoV-2 virus, the virus that causes COVID-19. This study will capture important data that will support researchers who are working on projects related to the COVID-19 pandemic.

This study builds on the information already captured by the previous COVID-19 questionnaire, including potential sources of exposure to the virus, such as those experienced by volunteers and frontline workers.

Antibody Study participation

Who is participating in the OHS COVID-19 Antibody Study?

In spring 2021, the OHS reached out to 12,000 Study participants, inviting them to participate in the COVID-19 Antibody Study. While COVID-19 has affected the lives of people all across Canada, it has had a greater impact on people who live in long-term care homes, people who are relatively new to Canada, and residents of certain parts of Canada, including major cities. Participants invited to take part in the COVID-19 Antibody Study were selected because they may be part of one of these groups. Selected participants were asked to use a home blood collection kit to provide a blood spot sample, and mail it back.

Can I participate in the COVID-19 Antibody Study if I have not had COVID-19? 

Yes. If you have received an invitation to participate in the COVID-19 Antibody Study, you can participate whether you have received a positive COVID-19 test result, or a COVID-19 vaccine. The questionnaire will ask if you have been tested for COVID-19 and what the results were, and whether you have received a vaccine. This information will be linked to your blood spot sample. 

I have a blood clotting condition. Should I provide a blood spot sample?

Your health and safety is paramount. We recommend that you not participate in the Antibody Study if you have:

  • A blood clotting condition (such as hemophilia or Von Willebrand disease).
  • Had chemotherapy within the last 4 weeks.
  • Undergone a double (bilateral) mastectomy. If you have had a mastectomy only on one side, you may perform the finger prick for the blood spot sample on the opposite hand.
  • Experienced fainting or vomiting due to a finger prick or the sight of blood.

Even if you decide not to take part in the Antibody study, you remain a valued member of the Ontario Health Study and we will contact you next time there is a new Study activity for you to undertake.

About antibody testing

What is a blood spot sample?

A blood spot sample is a process where a few drops of blood are collected on a piece of filter paper and dried. In this study, blood will be collected through a finger prick.

Why was I asked to give a blood spot sample?

Your blood spot sample will be used to conduct a serology test, also known as an antibody test.

What is serology or antibody testing?

Serological tests do not detect the SARS-CoV-2 virus (the virus that causes COVID-19) itself. Instead, they detect the antibodies your immune system produces in response to an infection or after receiving a vaccine. Serology tests are also known as antibody tests.

The immune response to a virus involves the creation of different types of antibodies produced at different stages of an infection:

  1. Early antibodies, called IgM antibodies, provide the first indication of the body’s response to an infection. These antibodies are not as specific and generally are not as long lasting, so interpreting their significance requires clinical experience
  2. IgG antibodies are specific to a virus, such as the SARS-CoV-2 virus. Early research results suggest these antibodies can be reliably detected 14 days after a person is infected with COVID-19 or receives a COVID-19 vaccine.

The OHS and CanPath are testing dried blood spots sampled from participants for IgG antibodies that are specific to SARS-CoV-2, the virus that causes COVID-19.

The relationship between antibodies and immunity to infection with SARS-CoV-2 is still not fully understood and continues to evolve rapidly.

Antibodies are present for an undetermined period of time after an infection has ended, or after a person has been vaccinated.

Serological studies, such as this one, aim to investigate these unknowns to provide a better understanding of COVID-19 and to identify how Canadians and public health officials can best respond to and manage the threat of the virus within our population.

How will my blood sample be used?

The blood spot sample you provide will be tested for antibodies to COVID-19. Once the lab analysis is complete, your sample will be returned for secure storage at the Ontario Health Study. Your sample may be used in the future by approved researchers for further health research, just like the biological samples some participants provided upon joining the OHS.

How is my privacy protected?

Your data will be protected using current security safeguards. These safeguards include keeping your personal information separate from study data, assigning a unique code number to identifying information, and only releasing coded data to approved researchers. 

Vaccines and the COVID-19 Antibody Study

Can the test detect antibodies from a COVID-19 vaccine? Can the test differentiate between antibodies from a COVID-19 exposure compared to antibodies from the vaccine? 

The lab tests we are running can detect antibodies developed after receiving a COVID-19 vaccine. The results you receive will not differentiate between antibodies resulting from a COVID-19 infection or a COVID-19 vaccine. Information about antibodies and the COVID-19 vaccine is evolving quickly. This study aims to help answer questions about COVID-19 antibodies and immunity.

Can I participate in the COVID-19 Antibody Study if I have received a COVID-19 vaccine? 

Yes. If you have received an invitation to participate in the COVID-19 Antibody Study, you can participate whether you have or have not received a COVID-19 vaccine. The questionnaire will ask if you have received a COVID-19 vaccine and this information will be linked to your blood spot sample.  

I have been vaccinated. Why should I still participate in the COVID-19 Antibody Study?

There is still valuable information we need to gather so we can learn more about the effectiveness of the vaccines, how long they remain effective, and if there is any change in the presence of antibodies over time.

If I receive the COVID-19 vaccine, do I have to withdraw from the COVID-19 Antibody Study?

No, you do not have to withdraw if you receive a vaccine – your data and samples are very valuable and will help researchers understand how long antibodies last following a vaccine dose! 

If I have been vaccinated for COVID-19 but my sample tests negative for antibodies, does this mean my vaccine did not work?

If you have received a COVID-19 vaccine but received a negative test result, antibodies may not have been present in the sample you provided to us. For example, if you received a vaccine, then provided a blood spot sample shortly thereafter, the antibodies would not have had time to develop by the time the lab tested your sample.

Providing your blood spot sample

How do I do the blood spot test?

Instructions to complete the blood spot sample collection will be provided in the mailed kit and can be found online here (PDF).

I was not able to fill all five circles with drops of blood. Do you still want my blood spot card?

Yes! It is better to fill a few circles with larger drops than try to fill all five with smaller spots. Please mail back your blood spot card as soon as possible, as we are not able to send you a second kit.

I didn’t receive/damaged my test kit. Can I get another one? 

We are sorry, but we are not able to send you another blood sample kit, given the complexities of the COVID-19 Antibody Study for our small team. We will close your participation in the Antibody Study, however you remain a valued member of the Ontario Health Study and we will email you the next time there are Study activities for you to complete.

Receiving your results

Will I get the results of the antibody testing?

Yes, you will get an email when your results are available to view online. It will take up to three months to receive the test results.

You will receive one of four possible results: a positive result confirming that there are COVID-19 antibodies in your blood, a negative result indicating that there are no COVID-19 antibodies in your blood, an inconclusive result indicating that there are some COVID-19 antibodies in your blood but not enough to meet the threshold for a positive result, or a technical failure result stating that an error occurred with the sample or analysis and the lab could not determine if COVID-19 antibodies were present.

The antibodies being tested for in this study become detectable approximately 10 to 14 days following infection or vaccination. Please consult your regular health practitioner if you have any questions about the findings from your blood spot sample.

What do my antibody test results mean?

The CanPath lab tests detect the presence of three antibodies against:

  • the spike protein which sits on the SARS-CoV-viral envelope (SmT1)
  • the receptor binding protein (RBD)
  • the SARS-CoV inner nucleocapsid protein (NP)

Antibodies to the spike (SmT1) and receptor binding domain (RBD) represent response to either prior infection or vaccine. Antibodies to the nucleocapsid proteins (NP) represent response to prior infection.

The lab set a threshold for positivity for each protein. A participant’s antibody test result is based on the combined result from the three tests. The lab labels a sample as ‘positive’ based on it passing a set cut-off value on 2 of 3 antibodies. It labels a sample as ‘negative’ or ‘Inconclusive’ when results come in below the lab’s set threshold for a positive result. A ‘technical failure’ result indicates that an error occurred with the sample or analysis and the lab could not determine if COVID-19 antibodies were present.

For privacy reasons, OHS staff do not have access to individual participant results.

In June 2021, CanPath published early findings about the Antibody Study, which noted that approximately 10% of participants who reported being vaccinated with a single dose of an mRNA vaccine and 30% of those vaccinated with a single dose of the viral vector vaccine (AstraZeneca) did not show signs of antibodies above thresholds differentiating them from the population at large. These results did not include data for the level of antibodies in participants who received double AZ doses or combo dose of AZ-mRNA, because, at that time, very few participants had received a 2nd dose.

View the CanPath early findings here

When can I expect to receive the results of the antibody test of my blood spot sample?

Study participants will receive an email when the results of their blood spot sample are available to view online via their OHS account, approximately three months after providing their sample.

Who will see the results of my blood spot sample?

The results of the serological (antibody) test obtained from your blood spot sample and any additional health measurements will be stored in the OHS database and in the CanPath national database. Your personally identifying information is only accessible to a small number of OHS staff.

Coded and de-identified questionnaire data and antibody test results will also be shared with the federal COVID-19 Immunity Task Force (CITF), which funded the study. A copy of your questionnaire and the test results from your blood spot sample will be stored in a database at McGill University. Only the information and test results collected as part of this study will be part of the CITF database. No other information you have provided to the OHS will be part of this database, and the CITF will not be able to link your data to you as an individual.

If I am notified that my sample tests positive for antibodies, how long will these antibodies last?

This is still unknown. Your participation in this study is important so we can learn more about COVID-19 infections, antibodies and immunity.

If my sample tests positive for COVID-19 antibodies, do I need to self-isolate or get tested for COVID-19?

No. Antibodies are not an indication of a current COVID-19 infection. If your sample tests positive for COVID-19 antibodies, this indicates that you have been infected with COVID-19 at some point in the past, or could be the result of a COVID-19 vaccine. If you are having COVID-19 symptoms unexplained by other health conditions, please follow up with your health practitioner, or contact Telehealth Ontario.

If you think you may have been exposed to COVID-19 and have been told to self-isolate, please wait until after this isolation period ends to participate in our study.

If I am notified that my sample tests positive for antibodies, does this mean I no longer need to practice protective measures (i.e. physical distancing, hand-washing, masking)?

At this time, it is unknown how long antibodies to COVID-19 may last. It is therefore important that you continue to follow local public health guidelines.

Will the antibody test detect antibodies from the variants of COVID-19?

Yes. The lab conducting our antibody testing continues to keep an eye on the new variants detected and will adapt the test as needed to capture antibodies from variants of the virus. The results you receive will not differentiate between antibodies resulting from a COVID-19 infection or a COVID-19 vaccine, nor will it specify which variant.