Antibody is a type of protein that protects body from foreign pathogens. SARS-CoV-2 antibody works against SARS-CoV-2, the pathogen of COVID-19. After contracting the virus or COVID-19 vaccination, SARS-CoV-2 antibody appears in the blood. The titer (level) of the antibody is considered to decline over time. The protective level of the antibody titer, i.e. the level of antibody that is high enough to protect a person from the virus infection or symptom development or worsening, is currently unknown.
There are several types of SARS-CoV-2 antibody, and each type has a different meaning. In the medical checkup, SARS-CoV-2 S-IgG is measured. This is an antibody that reacts with Spike protein of SARS-CoV-2.
| On the checkup report web, you may see: | SARS-CoV-2抗体の測定値（単位 AU/mL）は次の通りでした： IgG (S蛋白) [**your result**] ※検査会社が設定した基準値は50.0未満です（ |
| This means: | The figure that appears in [**your result**] is the titer of the SARS-CoV-2 antibody. Normal (no history of infection or vaccination of SARS-CoV-2): < 50.0 AU/mL. This can become positive after infection or vaccination. |
