Antibodies are created by the immune system after infection with a virus or bacteria. They are the proof that our immune system has fought a particular virus or bacteria before. For example, if you have received a vaccination against varicella (chicken pox), your blood will contain antibodies to varicella. This means the next time you’re exposed to varicella, your body will recognize the virus and quickly work to protect you against the disease.
Antibodies in the blood can be measured. This is a good way to tell if someone has been exposed to a disease before. For example, if you aren’t sure you had chicken pox as a child, doctors can draw your blood and look for antibodies. If there are no antibodies, it means you have not been exposed to the virus and a vaccine can be administered.
The same method can be used to tell if someone has had COVID-19, or the disease caused by the coronavirus (SARS-CoV-2). This disease also causes antibody to be made. However, because COVID-19 is new, there isn’t a reliable antibody test yet, so researchers are racing to develop a reliable antibody test.
This would be helpful for a few reasons. First, an antibody test could tell us which people have had the virus and recovered. It would also allow us to know who has not yet had it and might still be vulnerable. Tests could also help determine which areas of the country have achieved herd immunity, which means there are enough immune people in the population to slow the spread of the disease and protect vulnerable populations.
Not all antibody tests are equal, however, which is why it is taking so long to get them to the marketplace. A good antibody test must have several features:
- It must be easy to administer and to interpret. A perfect test could be done painlessly with results available in minutes.
- The test must be very affordable so that it could be used by everyone – this means it also must be easy to make millions of tests in a very short time.
- Finally, and most critical, the test must be accurate. If the tests reports a positive result, we need to know with almost 100 percent certainty that it is a true and accurate result. Similarly, if the test reports a person is negative, we need to know that the person is truly negative. These accuracy numbers are called the sensitivity and specificity of the test and should both be above 90 percent. So far, none of the tests available in the US have reached these benchmarks, so people should be careful when making decisions based on the results of the current antibody tests.
- Antibodies can be used to determine if someone has been exposed to a virus.
- Researchers are working to create a reliable antibody test for coronavirus.
- Knowing who has been exposed can help control the disease.