FAQs About the Different COVID-19 Tests and the COVID-19 Vaccine
Keeping up with the information about COVID-19 can be confusing. For months we have heard about COVID-19 testing but do you know the different types of testing, their benefits and limitations? What is the difference between PCR and Rapid Antigen testing? Our Clinical Educator has answered these questions and other frequent questions we hear from clients.
Please note that the answers provided may change as researchers and health authorities learn more about COVID-19. While TravelSafe is monitoring the situation closely, the answers below reflect policies and recommendations at the time of posting only. Always check with your local health authority for the latest recommendations.
What method of COVID-19 testing does TravelSafe use?
TravelSafe offers the PCR-based NAAT (Nucleic Acid Amplification Test) also known as the RT-PCR (Reverse Transcriptase Polymerase chain reaction) test. It is considered the “gold standard” of tests and is required by countries and airlines who require proof of a negative PCR COVID-19 test. Samples are collected from clients and are tested in an accredited laboratory in the Lower Mainland.
What is a COVID-19 Rapid Antigen test? (also known as a rapid lateral flow test)
Antigen tests detect the protein layer of the virus and can be used for diagnosis and screening. Samples can be taken from the respiratory tract (e.g., nasal swab), blood, or other bodily fluid. They usually provide faster results than molecular (e.g., PCR) tests but have a higher chance of missing an active infection (false negative).
Rapid Diagnostic Tests (RDTs), also known as Point of Care (POC) tests, are small disposable test kits that use a mucus sample from the nose or throat but can be analyzed directly on-site within minutes instead of being sent to a laboratory for analysis. While results are very quick, they are not as accurate as PCR tests. They are NOT recommended for individuals with symptoms of COVID-19. Individuals testing positive with a rapid test should arrange to have a repeat PCR test to confirm the results.
Are Rapid Antigen tests available in BC?
Rapid Antigen tests are being used in some provinces and territories in different places for different purposes (e.g., workplace screening). In BC, Rapid Antigen tests are not currently routinely available.
Why isn’t rapid antigen testing routinely available in BC yet?
Rapid antigen tests are less capable of picking up the virus and are considered less reliable than the gold standard PCR test, particularly if the antigen test is used on someone without COVID-19 symptoms. B.C. health officials continue to study their efficacy and their potential role in the province’s COVID-19 response but, to date, officials have not made them readily available in this province. Some experts argue that there is a role for rapid antigen testing despite their limitations (e.g., repeatedly screening asymptomatic individuals for COVID-19 at workplaces). Travel Safe will continue to monitor provincial health authority recommendations around rapid antigen testing.
I have tested positive for COVID-19 in the past. How long do I need to wait before I can be retested?
The Public Health Agency of Canada (PHAC) recommends that individuals who have recovered from COVID-19 generally should not be retested if they are asymptomatic. A PCR test may remain positive for weeks or months after recovery and may not necessarily represent a new exposure or re-infection. However, there have been rare reports of people getting re-infected as soon as 3 months following their initial diagnosis. Those who experience a new onset of symptoms should consult with their health care provider or local public health authority for guidance around re-testing.
If I have tested positive for COVID-19 in the past, should I still receive the COVID-19 vaccine? If so, how long do I need to wait before I can be vaccinated?
Yes, the BCCDC states that people who have gotten sick with COVID-19 may still benefit from getting vaccinated. People are eligible to get the COVID-19 vaccine whether or not they were previously infected. In B.C., see the BCCDC Vaccine eligibility webpage for more information. Visit your local authority (eg. Vancouver Coastal Health, Fraser Health) webpage for information about COVID-19 vaccination clinics and eligibility in your area.
Individuals infected with the COVID-19 (SARS-CoV-2) virus will have derived some protection from their infection. Those previously infected are recommended to wait at least 3 months after recovery before receiving the vaccination.
How does the COVID-19 PCR test differ from an antibody test?
A PCR test detects the genetic material (DNA) of the SARS-CoV2 virus and is typically used to diagnose an infection or to screen healthy people to ensure they do not have the virus. A respiratory sample (e.g., nasal swab) is taken by a nurse and sent to an approved laboratory for analysis. Results take hours to obtain (and practically may take several days depending on backlogs).
An antibody test (also known as a blood serology test) is used to detect antibodies (IgM and/or IgG) in your blood. Antibodies are made by the immune system to fight infections in response to the virus after you have been infected or vaccinated. IgM antibodies are produced early in the acute phase of infection and IgG antibodies are produced later. They can take several days or weeks to develop after an infection and may stay in your blood for several weeks or more after recovery. Hence, they are used to detect a past infection and are not recommended for diagnosing active COVID-19 infection. We do not yet know how long antibodies last in someone who has previously been infected or who has been vaccinated against COVID-19. Researchers also do not yet know whether the presence of antibodies means that you are immune to the coronavirus in the future.
How is an antibody test performed?
The test must be ordered by a health care professional. You will be given a lab requisition and instructed to take it to an approved laboratory where a small sample of blood is taken and later analyzed. The turnaround time is within 24h hours. Generally, antibody testing is being used for limited clinical and research uses and/or to investigate outbreaks. Some countries, including China, may require both a PCR and antibody test prior to travel.TravelSafe provides lab requisitions for antibody testing for individuals requiring the test for travel purposes only.
What does it mean if my antibody test is positive?
A positive or ‘reactive’ result tells you that you have antibodies from theSARS-CoV-2 (COVID-19) infection that happened in the past (or from being vaccinated).
Can I get re-infected with COVID-19 after testing positive for antibodies?
Researchers don’t yet know whether you can get COVID-19 again if you have antibodies. For some other infections, antibodies protect people from getting the infection again.
A positive antibody test result tells you that you have antibodies from aCOVID-19 infection that happened in the past OR from being vaccinated.For more information, see the BCCDC webpage on Antibody Testing. Please note, you cannot currently request an antibody test from your health care provider. TravelSafe offers lab requisitions for antibody testing for individuals who require the test for travel purposes only.
If I’ve received the COVID-19 vaccine, will I have a positive COVID-19 PCR test?
No, the vaccine will not result in a positive COVID-19 PCR test. The PCR test detects the COVID-19 virus and is used to diagnose infection. Rather, you may test positive for the antibody test due to the immune response that develops following vaccination.
Below is a table that summarizes the different COVID-19 tests, their limitations and benefits.
|Sample type||Throat or nasal swab (saliva also available in some areas)||Throat or nasal swab||Blood draw/finger prick|
(varies considerably depending on test brand)
|High||High accuracy for true positives
Higher rate of false negatives (less ability to accurately test those who are asymptomatic)
|Purpose of Test||Diagnosis/sometimes screening||Screening||Surveillance (past infection or vaccination status)|
|How long do results take?||1 – 7 days (depending on lab capacity)||1 hour or less||1 – 3 days|
|Analysis of sample||Lab||On-site||Lab or on-site|
|Limitations||– Results may be delayed
– Medical oversight required regarding return to work, travel, quarantine…
– Requires training to take the swab
– Best used for confirming a diagnosis
– Considered the ‘gold standard of tests’; however, may not detect everyone who is infected.
|– Less accurate than PCR tests
– Positive results highly accurate but negative tests may require confirmation with a PCR/molecular test
|Presence of antibodies does not mean the person is no longer contagious nor that they are immune from further infection.
– Antibody test CANNOT diagnose an active infection or show that you do not have COVID-19.
– Medical oversight required to interpret results.
If you require COVID-19 PCR/NAAT testing for work or occupational purposes, please call 604. 251-1975 or email us at firstname.lastname@example.org to arrange an appointment.