Immunization Tests vs. Tests for Past Infections

According to the Centers for Disease Control and Prevention (CDC) about 57% of people in the U.S. have never gotten Covid-19 (e.g. was not infected by SARS-Cove-2 virus). However, it is challenging to assess this estimation as many people were exposed to the virus but did not have symptoms. Antibody or serology tests look for antibodies in your blood that fight the virus that causes COVID-19. Some serology tests can differentiate a past COVID-19 infection from immunization tests e.g. vaccination, which means certain tests can detect antibodies that form after infection versus antibodies that are made from a vaccine. 

Can You Differentiate Between Vaccine and Infection-induced Antibodies?
If you look at antibodies against viral antigens like the nucleocapsid (N) protein, the vaccines that are used in the U.S. do not generate such antibodies. So, if you are vaccinated, and test positive for antibodies against the vaccine antigen target, such as the spike (S) protein, but negative for other antigens like N and RBD, then it would suggest you have produced vaccine-induced antibodies and were never infected with COVID-19. On the other hand, if you also test positive for antibodies other than the vaccine-induced antibody, such as the N protein, then that indicates you had a past COVID-19 infection that could have occurred before or after your vaccination. 

Other viral immunization
Like Covid-19 serological investigation, other serological tests can be useful also for other types of viral infections and vaccinations. If you are concerned about other viruses like chickenpox (Varicella Zoster Virus – VZV) or want to be sure you got the MMR vaccination (Measles, Mumps, and Rubella) specific antibodies tests for these viruses (MMR, VZV) and antigens can tell you your immunization status. Similarly, immunization tests for hepatitis A and hepatitis B are available to be purchased online (at this time there is no vaccination for hepatitis C).

Bacterial immunization
Tetanus is a life-threatening bacterial infection. The bacteria usually get into the body through a cut or wound in the skin. The bacteria make a powerful poison that causes muscles to contract uncontrollably in spasms. Tetanus is especially dangerous in young children and older adults. Diphtheria spreads when germs pass from an infected person to the nose or throat of others. Diphtheria causes a thick coating in the nose, throat, or airway and can lead to breathing problems, heart failure, paralysis, or death. Tetanus and Diphtheria Antibody Profile test assesses immunity against tetanus and diphtheria by determining levels of circulating antibodies to tetanus and diphtheria toxins or to measure the immune response, postvaccination, in people suspected of immunodeficiency disorders. 

When Should I take antibody tests to check my past infections and immunization?
Antibodies are proteins created by your immune system that help you fight off infections. They are made after you have been infected or have been vaccinated against infection. Vaccination is a safe, effective way to teach your body to create antibodies. Antibody tests normally are not used to diagnose a current infection because it can take 1 to 3 weeks after the infection for your body to make antibodies. Antibodies can protect you from getting those infections for some period afterward. How long this protection lasts is different for each disease and each person. People with an immune deficiency or people who were vaccinated in their childhood and are not sure if they are still immune can check their immunity.

Conclusion
You can learn your overall immunity with serological antibody tests that checks if you have had an infection or are immune to a disease. Immunity can occur from having a vaccination or contracting the disease. Several immunization test panels for viral infections including SARS-Cov-2, Measles, Mumps, Rubella, chickenpox, and hepatitis are available to purchase online without a doctor. Similarly, Tetanus and Diphtheria Antibody Profile are available online and can be used to test your immunity to these bacteria.

Is there a way to know if you’ve never had Covid-19?