The COVID-19 vaccination is being launched across Australia. Therefore, health officials are eager to dispel myths about vaccines, including any impact on COVID tests.
Do vaccines provide COVID or make the test positive for COVID? Does the vaccine affect other tests? Do we still need to have the COVID test if we have symptoms, even after receiving the injection? And will we still need the COVID test, once the population is vaccinated again?
We analyzed the evidence to answer five common questions about the impact of COVID vaccines on tests.
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1. Will the vaccine give me COVID?
The short answer is no. “That’s because vaccines approved for use so far in Australia and elsewhere do not contain the live COVID virus.
The Pfizer / BioNTech vaccine contains an artificially generated portion of viral mRNA (messenger ribonucleic acid). This carries specific genetic instructions for your body to produce the “peak protein” of the coronavirus, against which your body assembles a protective immune response.
The AstraZeneca vaccine uses a different technology. It packs the viral DNA into a “carrier” viral vector based on a chimpanzee adenovirus. When this is delivered to your arm, the DNA tells your body to produce the spike protein, once again stimulating an immune response.
Any side effects of the vaccine, such as fever or fatigue, are usually mild and temporary. These are signs that vaccines are working to boost your immune system, rather than signs from COVID itself. These symptoms are also common after routine vaccinations.
2. Will the COVID vaccine make the test positive?
No, a COVID vaccine will not affect the results of a COVID diagnostic test.
The current gold standard diagnostic test is known as the nucleic acid PCR test. He looks for the mRNA (genetic material) of SARS-CoV-2, the virus that causes COVID-19. This is a marker of current infection.
This is the test that the vast majority of people do when they line up at a drive-through testing clinic or go to a COVID clinic at their local hospital.
Yes, the Pfizer vaccine contains mRNA. But the mRNA he uses is only a small part of the entire viral RNA. It also cannot make copies of itself, which would be necessary for it to be in sufficient quantity to be detected. Therefore, it cannot be detected by a PCR test.
The AstraZeneca vaccine also contains only part of the DNA, but is inserted into an adenovirus carrier that cannot replicate, so it cannot cause infection or a positive PCR test.
Read more: How Pfizer and Moderna mRNA vaccines work, why they are an innovation and why they need to be kept so cool
3. How about the antibody test?
While the PCR test is used to detect the current infection, the antibody test – also known as a serology test – detects previous infections.
The labs look to see if your immune system has raised antibodies against the coronavirus, a sign that your body has been exposed to it. As it takes time for antibodies to develop, a positive test with an antibody test may indicate that you have been infected for weeks or months.
But your body also produces antibodies in response to vaccination. That’s how he can recognize SARS-CoV-2 the next time he finds it, to protect him from serious COVID.
So as COVID vaccines are launched and people develop a vaccine-induced antibody response, it can be difficult to differentiate between someone who has had COVID and someone who was vaccinated a month ago. But this will depend on the serology used.
Read more: Antibody tests: to control the coronavirus, we need to know who has had it
The good news is that antibody testing is not as common as PCR testing. And it is only requested in rare and limited circumstances.
For example, when someone tests positive with PCR, but is a false positive due to the characteristics of the test, or has fragments of virus remaining in the respiratory tract of an old infection, public health experts can order an antibody test to see if that person has been infected in the past. They can also order an antibody test when tracking case contact with an unknown source of infection.
Read more: Why can’t we use antibody tests to diagnose COVID-19 yet?
4. If I get vaccinated, will I still need a COVID test if I have symptoms?
Yes, we will continue to test COVID while the virus is circulating anywhere in the world.
Although COVID vaccines appear promising in preventing serious illness or death, they do not provide 100% protection.
Real-world data suggests that some vaccinated people can still catch the virus, but they usually only contract minor illnesses. We are not sure whether vaccinated people can potentially pass it on to others, even if they have no symptoms. Therefore, it is important that people continue to take the test.
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In addition, not everyone will be eligible to receive a COVID-19 vaccine. For example, in Australia, current guidelines exclude people under the age of 16 and those who are allergic to the ingredients of the vaccine. And although pregnant women are not prevented from receiving the vaccine, it is not routinely recommended. This means that a proportion of the population will remain susceptible to contracting the virus.
We are also uncertain about the effectiveness of vaccines against emerging variants of SARS-CoV-2. Therefore, we will continue testing to ensure that people are not infected with these strains.
Read more: UK, South Africa, Brazil: a virologist explains each variant of COVID and what they mean for the pandemic
We know that testing, early detection of new cases and contact tracking are the main components of the public health response to COVID and will continue to be a public health priority.
A minimum number of daily COVID tests is also required so that we can be sure that the virus is not circulating in the community. For example, New South Wales plans to run 8,000 or more tests a day to maintain that peace of mind.
Continuous surveillance and high testing rates for COVID will also be important when we enter the flu season. That’s because the only way to differentiate between COVID and influenza (or any other respiratory infection) is through testing.
5. Will the test for COVID be interrupted over time?
Our approach to COVID testing is unlikely to change in the immediate future. However, as the COVID vaccines are launched and as COVID is likely to become endemic and remain with us for a long time, the acute pandemic response phase will end.
Therefore, the COVID test can become part of the management of other infectious diseases and how we respond to other ongoing health priorities.
Read more: coronavirus can become endemic – see how