SARS-CoV-2 spike protein-specific IgG antibody test
Several antibodies against a given virus are produced during an infection, as several different proteins of the virus can trigger an immune response. Individual differences can be seen in the type and amount of antibody produced, and for how long it can be detected following an infection. Manufacturers of commercially available reagents test for different types of antibodies to detect an immune response, so the results may vary. Tests for antibodies to the COVID-19 nucleocapsid protein and spike protein are also currently available.
In COVID-19, both types of antibodies appear in the blood. However, the vaccines used to prevent the infection differ in their ability to elicit an antibody response. This is determined by the technology of the vaccine. In the case of vaccines that prevent only the production or entry of the spike protein (e.g., mRNA and the vector vaccines), the immune response after vaccination can only be measured by tests for antibodies against the spike protein. Appearance of the IgG antibodies is expected 7-15 days after an infection.
Indications for the SARS-CoV-2 IgG spike protein antibody test:
- whether there has been a prior infection
- whether specific antibodies have appeared after vaccination, in which case it is recommended to take a sample after the expected time required to develop full protection, as described in the vaccination documentation (e.g., for Pfizer-BioNTech’s Comirnaty COVID-19 vaccine, at least 7 days after the 2nd vaccination)
The test is not suitable for answering the following cases:
- determination of current infectivity - this requires a PCR test from a respiratory sample!
- it does not separate a previous infection from a currently active infection!
- exclusive proof of protection - the test provides information on the number of antibodies present, which is not always directly proportional to protection. It indicates that an immune response has been elicited, which will certainly help in defense against an infection, but many other factors also play a role in the immune system’s overall defense.
Be sure to consult your doctor for a proper interpretation of the result, as this requires additional information, such as previous COVID-19 infection, test results, vaccination history.
For further information and to make an appointment, phone: +36 1 377 6737.