As more people have received their COVID-19 vaccines, I am receiving questions about checking antibody levels. People want to measure their antibody status as reassurance that the vaccine worked and they are protected from COVID infections. Let’s talk about antibodies and clear up some common misconceptions.
Antibodies are a type of protein made by our white blood cells. There are several different classes of antibodies with a variety of different roles in our immune system. The antibody in our discussion is designed to attach to a portion of the COVID-19 virus called the spike. The spike attaches to human cells and allows the virus to infect that cell. The antibody produced after the COVID-19 vaccine blocks the virus’ spike from attaching to our cells. This frontline defensive attack takes place with antibodies found in the secretions of our eyes, noses, mouths, and lungs. If we are exposed to more virus particles than we have antibodies available, our frontline antibody defense system is overwhelmed and an infection ensues. It is important to note that the antibodies present in our blood stream (and that are measured by lab testing) are not the ones responsible for defending us against infection. So measuring the antibody levels in our blood does not exactly tell us about our ability to avoid infection.
So what about the vaccine-induced antibodies in our blood stream? After an infection has occurred, infected cells begin manufacturing massive copies of the virus which then, in turn, infect even more human cells. Antibodies in our blood attach to the freshly-made COVID-19 viruses and prevent them from attacking cells in our bodies. This is where the Delta variant becomes dangerous. It reproduces so quickly it outpaces our ability to produce enough protective antibodies.
There is even more to the story. A special kind of white blood cell called T-cells are primed by the COVID-19 vaccine to recognize and destroy infected cells in our bodies. Destroying infected cells prevents those cells from making more COVID viruses and, therefore, limits the severity of the infection. This is an important way the vaccine reduces the number of hospitalizations, ICU patients and deaths.
As you can see, the discussion around COVID-19 antibodies is very complex. Measuring antibody levels shows only a small part of a large and complex picture and does not fully answer our questions about the risks of COVID transmission, infection, and death.