These are questions many people gone through coronavirus wondering about - how do we know that are we protected from Covid-19? Vaccinated  are also wondering whether they are already immune to the virus.

Antibody tests may have many answers and can help with all of these questions, although they don't provide absolute clarity about levels of immunity.

There are two main kinds: tests that measure whether antibodies are present at all, and others that assess how well those antibodies perform against the virus.

First are mainly reliable and can establish whether you have had the coronavirus or not.

The second, known as neutralising tests, blood serum is brought into contact with parts of the coronavirus in the lab to see how antibodies work to to keep the virus out.

While the test doesn't offer absolute certainty, it's safe to say that a positive neutralization test almost always means you're protected.

That means even simple antibody tests provide a certain degree of protection, although how much they can tell you is limited. For the moment the level of immunity is not possible to determine with precision by the amount of antibodies.

But what about the prices? While this varies from country to country, in much of Europe, antibody tests, can cost around 18 euros (the equivalent of 22 dollars), while neutralization tests are between 50 to 90 euros (60 to 110 dollars).

There are also tests for home use, where you take some blood from your fingertip and send it in for lab analysis or drip it directly onto a test cassette - similar to a rapid antigen test that tests for acute corona infection.

What actually antibody test is looking for?

 The body's fast reaction forces against the virus are the IgA and IgM antibodies. They're quickly formed but the levels of them in your blood after an infection also fall more quickly than the third group of antibodies.

These are the IgG antibodies, formed by "memory cells", some of which can remain in the body for a long time and remember that the Sars-CoV-2 virus is an enemy.

The body does not produce IgG antibodies until a few days after infection. So if you're testing for this type of antibody, as is the norm, experts say wait two weeks after the infection at least.

Meanwhile, if the test is looking to establish whether there are IgM antibodies, for example, it may come out negative even just a few weeks after infection. But this still doesn't mean you don't have any protection in you.

If one have relatively robust T-cell immunity, it ensures that he/she get less sick or not ill at all, despite having fewer or no antibodies.

In theory, everyone who wants to can have their blood tested for T cells, depending on their location, as various lab physicians offer T-cell tests.

So when does it even make sense to have an antibody test?

Scientists advise that it makes sense particularly for people with an immune deficiency or who take immunosuppressant drugs, after the second vaccination to see how high the antibody level is.

Apart from them anyone who wants an assessment of immune protection against the coronavirus should opt for a neutralization test.

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