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Can I participate if I have received or plan to receive a COVID-19 vaccine booster?

Yes! Our survey has been updated to capture booster information. For most accurate results, it is best to wait at least 14 days after your booster to get your antibody test.

Why should I participate?

There is currently little known about COVID-19 antibodies, including how long they last in the blood and/or what amount of protection they provide against future infection. Getting tested will help Texans understand how many people may have been infected and did not show symptoms, and how many Texans currently have COVID-19 antibodies (either from infection or vaccination) and how long they last. This will help inform decisions about vaccination schedules to help Texas fight COVID-19. The addition of the S-test will also allow you to evaluate your vaccine-induced immune response.

Who can participate?

Texans age 5-80. Anyone can participate, even if they have never been tested for COVID-19 or have tested positive or negative for COVID-19 in the past. We suggest waiting at least 14 days since a positive confirmed COVID-19 viral test before getting your antibody test. You can participate even if you have been vaccinated or plan to receive the vaccine soon. Antibody status of vaccinated individuals provides important information about vaccine-induced immunity. Fully vaccinated means having 2 doses of either Pfizer or Moderna vaccines, or 1 dose of Johnson & Johnson vaccine AND waiting 2 full weeks after the final dose from any vaccine.

Can I still participate in Texas CARES if I have gotten the vaccine or plan on getting the vaccine?

Yes! Our testing now detects both vaccine-induced antibodies as well as those developed after natural infection. Both vaccine-induced immunity and natural immunity are important to understanding where we stand in the progression to herd immunity. We encourage all participants to get the vaccine when it becomes available to you.


How will I get my results?

Your results (positive or negative for COVID-19 antibodies) will be texted to you 2-5 days after you get your blood drawn at CPL. You can access a full report on CPL’s portal after you receive the text message from Texas CARES. If your results are not loaded in the portal, please call the Sonic MyAccess customer service group at 844.280.8484. 

Parents or Guardians may create an account for their minor child, aged 17 or younger, by clicking on the link below. As part of the registration process, you will be asked to complete, sign, and submit a Record Request (RR) Form along with proper identification via email, fax or mail. Once the completed form is received and patient identity has been verified, the account will be activated and the requester will be notified via email. For assistance with this process, please call 844.280.8484 to speak with one of our dedicated patient record specialists who can answer additional questions or assist with completing the Record Request (RR) form

What does a negative antibody test result mean?

A negative N-test antibody test means that you most likely have not been infected with the virus in the past. Antibodies may not be present among those tested early in the infection before antibodies develop. In some persons, antibody levels may become non-detectable after previously being present. If you currently have symptoms or have come into recent close contact with someone with COVID, please seek a virus test with your local public health department.

S-test detects antibodies from a past COVID-19 infection AND/OR vaccination. Vaccine-induced immune response time varies. It typically takes up to 2 weeks after the second dose of the available 2-dose mRNA vaccines or 14-28 days after of one dose of the Johnson & Johnson vaccine to achieve full immune response. Our program offers up to 3 tests over a 6-month period so you can know how your immune response changes over time. You will receive your next survey link 3 months after your test, which will generate your next order number.


What does a positive antibody test result mean?

The presence of anti-SARS-CoV-2 antibodies (positive N-test) indicates a previous infection and possibly at least some degree of protection against future SARS-CoV-2 infection.  However, until the durability and duration of immunity are established, it cannot be assumed that individuals who test positive for SARS-CoV-2 antibodies, including total antibody, IgM, IgG, or IgA, are protected from future infection.

Asymptomatic persons who test positive by serologic testing without recent history of a COVID-19 confirmed or compatible illness have a low likelihood of active infection and should follow the CDC’s general recommendations to prevent infection with SARS-CoV-2. They should continue with normal activities, including work.

Persons who have had a COVID-19 compatible or confirmed illness should follow the CDC’s guidance regarding when to resume normal activities, including work, regardless of the presence of antibodies.

There should be no change in clinical practice or use of personal protective equipment (PPE) by health care workers and first responders who test positive for SARS-CoV-2 antibody.

A (positive S-Test): detects antibodies from a past COVID-19 infection AND/OR vaccination.


What do my CPL test results mean?

"COVID-19 Antibodies, Spike Protein" (S-Test): detects antibodies from a past COVID-19 infection AND/OR vaccination

"SARS-CoV-2 Total Antibodies" (N-Test): detects ONLY antibodies from a past COVID-19 infection

Results clarification

We are unable to provide medical advice. Please follow up with your primary care provider if you have additional questions about your results.

What does the index number for the "COVID-19 Antibodies, Spike Protein (Quantitative)" (S-test) mean?

The S-Test portion of Texas CARES' total antibody test provides a value that is linked to the quantity (number) of antibodies present in your system produced in response to your COVID-19 vaccine or past infection.

At this time, the research community does not have enough information to interpret ranges (i.e. what a 700 value means for immunity protection compared to a 1,200). We are still learning and gathering more information to explain what the numerical value indicates in relation to strength of immunity and length of immunity. We are unable to provide medical advice. Please follow up with your primary care provider if you have additional questions about your results.

However, you are able to: 

  1. Confirm whether or not you currently have antibodies present
  2. Track your personal S-test antibody index value over time (S-test positive range = 0.8-2500 U/mL) via the three free antibody tests Texas CARES offers 
  3. Contribute data through the Texas CARES survey to help the research community understand how to interpret these numerical ranges in the future

What does the "SARS-CoV-2 Total Antibodies Quantitative" (N-test) COI number mean?

The N-test cutoff index (COI) is the cutoff measurement used to identify antibody presence. Texas CARES uses two tests. The N-test is a qualitative test that measures total antibody (IgM, IgG, IgA).

COI* < 1.0 = non-reactive

COI ≥ 1.0 = reactive


Information from Roche (the test manufacturer)

Interpretation of the results:

Results obtained with the Elecsys Anti-SARS-CoV-2 assay can be interpreted as follows:

The magnitude of the measured result above the cutoff is not indicative of the total amount of antibody present in the sample. The individual immune response following SARS-CoV-2 infection varies considerably and might give different results with assays from different manufacturers. Results of assays from different manufacturers should not be used interchangeably.

If I have gotten the vaccine, does a negative antibody result mean the vaccine didn’t work?

No. Immune response time varies. It typically takes up to 2 weeks after the second dose of the 2-dose mRNA vaccines available or 14-28 days after one dose of the Johnson & Johnson vaccine to achieve full immune response. Our program offers up to 3 tests over a 6-month period so you can know how your immune response changes over time. You will receive your next survey link 3 months after your test, which will generate your next order number.

What COVID-19 antibody test is used?


Roche Elecsys Anti-SARS-CoV-2 S (semi-quantitative assay that detects antibodies from vaccination or past infection)

Roche Elecsys Anti-SARS-CoV-2 (qualitative assay that only detects antibodies from past infection)

More information about these tests:


Clinical overview of both tests

What is the margin of error?

Roche Elecsys Anti-SARS-CoV-2 S (vaccine-induced & natural immunity)

Clinical specificity: 100%

Positive percentage agreement: at > or = 15 days post PCR confirmation: 96.6%

Negative Percent Agreement: 99.98%



Roche Elecsys Anti-SARS-CoV-2 (natural-induced immunity)

Clinical specificity: 99.8%

Clinical sensitivity at > or = 14 days post PCR confirmation: 99.5%

Antibodies may not be present among those tested early in illness before antibodies develop or among those who never develop detectable antibodies following infection. We recommend waiting 14 days after a positive PCR COVID-19 test before getting tested for antibodies. https://diagnostics.roche.com/us/en/products/params/elecsys-anti-sars-cov-2.html

Will my results be shared with anyone?

Your personal results will not be shared with your employer, organization, or academic institution.

Why up to 3 tests?

Texas CARES is a longitudinal survey that aims to identify the specific protection from future COVID-19 infection provided by the anti-SARS-CoV-2 antibodies as well as the duration of the presence of antibodies and a degree of protection. If you have antibodies present at T1, your T2 and T3 will identify how long those antibodies remain in your blood. The addition of the S-test will help us determine how long antibody response from vaccination lasts in our population.

How will I know when to get my second and third tests?

You will receive a text reminder with a personalized link to the T2 (3 months after your first test) and T3 surveys (3 months after your second test) that will generate your new order number to bring to CPL for your T2 and T3 draws. Please email us at texascares@uth.tmc.edu if you have not received your text message 3 months after your last antibody test.

Can I participate if I am already enrolled in another study?

You can still participate in the Texas CARES program if you are already enrolled in another study.

What is an antibody?

An antibody is a protein formed by your body in response to a specific foreign substance, such as a virus, that helps your body fight infection. Presence of an antibody in the blood can help identify a past infection. Antibodies are also produced in response to vaccination.

What is the difference between an antibody test and a viral test?

Antibody tests identify a past infection, while viral tests identify a current viral infection.

What is the difference between SARS-CoV-2 and COVID-19?

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a strain of coronavirus that emerged in 2019 that causes an acute respiratory disease named coronavirus disease 2019 (COVID-19). SARS-CoV-2 is the virus that causes COVID-19

What are the steps to enroll?

Complete the consent and survey at https://go.uth.edu/txcares.

Your lab order is automatically generated by our system and sent to a CPL lab unless you are a patient or employee at a participating clinic. You will receive a confirmation text upon completion of the survey that contains your order number.


Do I need to pay for my COVID-19 antibody test at the CPL?

No, participation is free. Expenses are covered by Texas CARES

Do I need to schedule an appointment?

No, but we recommend checking the hours of operation for the CPL locations near you at https://www.cpllabs.com/locations/ before going to the lab. No appointment needed.

What do I need to bring to CPL?

Your picture ID and your confirmation text which contains your Requisition ID# 255799-XXXXXXXX

Where can I go for updates and more information about COVID-19?

The most-up-to-date information is available on COVID-19 is available at the CDC general webpage: https://www.cdc.gov/COVID19.