Can I get back to school or work with an antibody test?

Governments around the world want antibody tests to inform them who can be protected from reinfection and return safely to normal activities.

The idea of ​​providing proof of exemption to allow workers to return to work has been considered in many countries, including the United Kingdom and Italy. Officials from other countries such as Chile, France and Germany have already taken this step. They rely on what’s called an antibody test, a blood test to determine if someone has been infected with a coronavirus.

We welcome you to know if you had antibodies, and of course, we are happy to be able to resume something like normal life.

But like the other tests, they were not perfect and their accuracy was problematic. Here’s what you need to know.

What is an antibody?

Antibodies are small Y-shaped proteins that are produced by specific cells of the immune system when antigens such as pathogenic microorganisms such as SARS-CoV-2 virus enter the body.

Antibodies help fight off the antigens that caused their production. But it does not kill or dismantle the antigen. Just bind or attach. Also, antibodies bind only to the antigen that caused them to be produced. Therefore, when infected with the SARS-CoV-2 virus, immune cells begin to produce antibodies that bind only to the SARS-CoV-2 virus. These antibodies do not bind to other viruses or antigens.

By binding to the antigen, the antibody can contain the virus in several ways. Some viruses lose the ability to enter cells that can grow when antibodies are attached. Some “attached antibodies” activate the complement system, a group of proteins that circulate in the blood and can destroy antigens when activated. The attached antibody also acts as a handle that makes it easier for immune cells to grab and swallow the antigen.

What is an antibody test and how does it work?

Immune cells produce five types of antibodies: immunoglobulin M (IgM), immunoglobulin G (IgG), immunoglobulin A (IgA), immunoglobulin E (IgE), and immunoglobulin D (IgD). There are blood tests that can identify and quantify these antibodies. Most of these existing blood tests measure either IgM or IgG.

Immune cells produce large amounts of IgM when new antigens enter, but IgM production declines rapidly so that significant levels persist in the blood for only three months. IgG, on the other hand, is not as abundantly produced as IgM, but remains circulating for many years. Therefore, a positive IgM result indicates that the person is currently or recently infected, and a positive IgG result and a negative IgM result indicate that the person may have been infected in the past.

As a general rule, no antibody test is used to determine if someone has an active Covid-19 infection. This is because it takes more than a week for immune cells to produce enough antibody to be detected by these tests. The test performed in the suspected case of Covid-19 is a swab test in which a 6-inch long cotton swab is inserted deep into the nose or throat to obtain a tissue sample. The swab is then sent to the lab for molecular testing.

One use of the Covid-19 antibody test is to identify donors for convalescent plasma therapy. This procedure involves transfusing plasma (a liquid component of blood) from a donor into a severely ill Covid-19 patient to enhance self-generated antibodies. Test for Covid-19-positive patients who have recovered from the disease or are asymptomatic. If they still have high levels of antibodies, they are a suitable donor.

Antibody tests are also used to find out how many people in the population are already infected with Covid-19 and are asymptomatic or have only mild symptoms. This will allow public health workers to identify the true infection rate, predict the likely future course, and plan the interventions needed to control it in a particular population.

If you have antibodies, you have immunity, right?

necessarily. In general, encountering a virus confers long-term, often lifelong, immunity to the virus. This applies to measles, polio, and some other viruses. Therefore, if you are IgG positive for Covid-19, you may already be immune to Covid-19. However, as WHO recently stated, there is currently no evidence that people with Covid-19 antibodies are protected from a second infection. The simple truth is that there are too many unknowns about the nature of Covid-19, including whether previous encounters with the virus provide any immunity.