Our very own Dr. Tammi Shlotzhauer explains why this can happen.

Dr. Shlotzhauer is the Assistant Medical Director of Rochester Clinical Research as well as a practicing rheumatologist. She is board-certified in both internal medicine and rheumatology.

By Dr. Tammi Shlotzhauer

To understand this, you need to understand a little about immunology, viruses, and vaccines

First, to fight pathogens like viruses, your body makes antibodies against proteins that make up the germ. Viruses, like the coronavirus, are made up of several different proteins. When you get infected, the body first makes antibodies of the IgM type against many different parts of the virus. IgM antibodies rise early in the infection and then disappear over a few weeks. Your body then makes IGG antibodies against the viral proteins but a bit slower. These, however, stay elevated for months to years, conferring immune “memory” and thus protection or “immunity” to the virus.

Vaccines are historically created by identifying a protein in the virus and creating a way to deliver that protein to you so that you can make protective antibodies. Conventional vaccines contain either an injured virus or a chosen viral protein attached to some delivery system.  The new RNA vaccines direct your body to make the chosen protein by following the RNA “recipe”. With the COVID-19 vaccines, the chosen protein is the “spike protein”.

Hence, what all COVID-19 vaccines have in common is…. in one way or another …your body receives (or makes) the coronavirus spike protein in some form. And, you make protective antibodies against the spike protein giving you immunity to coronavirus.

Now, recall that the coronavirus has more than just one protein.  It also contains a protein called “nucleocapsid”. So, when antibody diagnostic tests were developed, manufacturers devised varied tests:

Some detected the spike protein antibody.

Some detected the nucleocapsid protein antibody.

Some detected both the spike protein and the nucleocapsid protein antibodies.

They also found that the antibody test against nucleocapsid protein picked up earlier cases of COVID-19 infection making it a more “sensitive” test (picks up more cases).

When there wasn’t a vaccine, of course, all positive tests were from infected (or previously infected) patients because they made antibodies against all of the virus proteins. Now, people who have had the vaccine will test positive with the tests that look only for Spike protein antibodies. However, they will test negative for tests that only test for the nucleocapsid antibody!

Because places like the Red Cross or hospitals are more interested in determining if an individual is infected, they will more than likely use the nucleocapsid test. This test was not devised to see if a vaccine had been given, but rather to see if someone had Covid. The spike protein antibody test would not differentiate between these two situations.

The bottom line- don’t get an antibody test to see if the vaccine “worked” or if you are getting a placebo in a clinical trial. You have a very good chance of getting an incorrect answer.