Antibody Testing

An Antibody Test, also known as a Titer, is a blood test that determines if a person has the antibodies that are presumed to provide immunity to an infectious disease. Workers in certain industries may be required to take antibody tests to demonstrate to an employer that they are not susceptible to catching illnesses which are considered dangerous in their line of work, especially because of the risk of transmission to other staff or clients.

Antibody tests, also known as titer tests, are required for many employees on a pre-employment, periodic, or annual basis to ensure the safety of co-workers and the public with whom they interact. Antibody blood tests are a component of occupational health screenings which indicate if a person is immune to certain common diseases. Generally, if an antibody tests shows that a person is not immune to a particular illness, they can be required to get an immunization through their job if one is available.

Regarding the pandemic, It is expected that antibodies to COVID-19 will confer immunity to the novel coronavirus much like antibodies confer immunity to other infectious diseases like measles, mumps, and varicella (chicken pox). However, it is still uncertain if antibodies do provide immunity to COVID-19, and even if they do, it has not yet been established how long that immunity will last.

Antibody Testing

Antibody Tests for Employees

Antibodies are the proteins that form part of the immune system. They help fight off bacteria and viruses that can cause disease. A blood test which can detect antibodies is known as an Antibody Titer Test. Employers use antibody testing to check if staff have immunity to various diseases.

A titer blood test can see if antibodies have developed after an infection has appeared. Additionally, a titer test also determines if a person has retained immunity to a disease in the years after having received an immunization.

Although most people have been immunized against common infections like Measles, Mumps, and Rubella, the antibodies which protect a person after vaccination may fade over time. The titer blood test is a way of checking if a person still has enough antibodies to protect themselves. If a person’s immunization record is lost, out of date, or unreliable, a titer blood test is a foolproof way to discover which immunizations are still current, and which vaccinations they need to get.

Common antibody titer blood tests can check employees for hepatitis A, B and C, varicella (chickenpox), and MMR antibodies (measles, mumps and rubella), ensuring that they’re protected and, if not, indicating that a vaccination is required before beginning or continuing employment.

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Which Industries Need Antibody Testing for Employees?

Antibody tests are frequently used in the healthcare industry, to ensure that people working with vulnerable populations like the sick or elderly are protected against every necessary disease. This includes nursing homes, hospitals, medical clinics and home care providers, including vendors that come into the facility and interact with staff.

Vaccinations for chickenpox are also required for teachers and students, childcare workers, international travelers, military personnel and both inmates and workers at correctional institutions. The varicella titer test, which tests for the varicella-zoster virus (chickenpox and shingles) may be used in these cases, to determine which employees are currently immune versus those which require a vaccination.

According to OSHA, any employees who may come into contact with blood or other potentially infectious materials at their workplaces have a risk of exposure to the Hepatitis B virus. Employers at these types of facilities must offer vaccinations to their workers, and therefore, may require employees to take a titer blood test for Hepatitis B to determine the need for a vaccine.

In addition to healthcare workers and first-aid personnel, emergency responders, morticians, correctional officers and laundry workers in commercial laundries within healthcare or public safety institutions are also often required to get antibody blood tests.

Antibody Tests and COVID-19

Due to the COVID-19 pandemic, there has been a lot of discussion about antibody tests. As employees return to work, the EEOC has determined that since coronavirus is “a direct threat,” employers have the legal right to test their employees before allowing them to return to work. This includes COVID-19 antibody tests, specifically the IgG COVID-19 antibody test.

IgG COVID-19 antibody tests do not indicate if someone is currently ill or contagious, because the IgG antibodies typically do not show up in someone who has recently become ill. It normally takes up to three weeks for an infected person to develop IgG antibodies. Therefore, this test’s purpose is to determine if someone had COVID-19 in the past. While it is expected that the IgG antibodies will confer immunity to the novel coronavirus, it is uncertain if someone who previously had COVID-19 can get it again. Even if the antibodies do provide immunity, it is not yet known how long that immunity will last.

Normally, employers use private companies for antibody testing, which send their specimens to private, certified laboratories. The Centers for Disease Control and Prevention (CDC) also developed its own serologic (antibody) test. They are using this blood test to help evaluate the efficacy of antibody tests developed by private labs.

COVID-19 Antibody Test

Antibody Testing and Public Health

On an individual level, an antibody test looks for antibodies in the blood. Your immune system makes antibody proteins to help fight infections. If you were exposed to COVID-19, an antibody test will show whether or not you’ve developed antibodies against SARS-CoV-2, the virus that causes COVID-19. An antibody test cannot tell you whether you have a current COVID-19 infection.

On a population level, antibody testing can give researchers a sense of how many people have been exposed to and infected by COVID-19. In the future, antibody testing may show whether someone has immunity against COVID-19, meaning that they cannot get infected again. If antibodies make people immune to COVID-19, it can help inform leaders and public health officials about whether the population has reached herd immunity. Herd immunity is when a large percentage of a population has become immune to COVID-19, which can protect those people who are not immune.

Antibody vs. Antigen Blood Test

Antigen tests can tell if a person is actively fighting a current infection. An antigen is a foreign substance that will cause the body’s immune system to produce antibodies to fight off an infection. Antigen tests can be used to detect if a potentially infectious germ is currently present in a person’s body. Rapid antigen tests can be used to test for malaria, streptococcal sore throat and influenza. The P24 antigen test can diagnose HIV. Antigen tests can also detect Hepatitis.

As with titer blood tests, antigen tests may be administered in workplace environments where clients, patients, or co-workers may be vulnerable to catching contagious illnesses.


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