Antibodies, Antigens and You: What Comes Next After Vaccinations?

The elusive search for Covid-19 herd immunity continues as global vaccination rates rise higgledy piggledy across the world.

In developed countries with ample vaccine supplies such as the US, ‘breakthrough infections’ of vaccinated people is now a headline topic. Meanwhile, north and south Europe both report a resurgence of infections. Israel, which leads the world for Covid-19 vaccinations, is reinstating social curbs.

If it wasn’t before, what is now clear from the data is that emergency vaccines do not prevent transmission from occurring but do prevent the worst symptoms of Covid-19 from manifesting.

Thus they reduce the number of severely ill people who require hospitalisation and alleviate pressure on exhausted healthcare frontliners.

In short, emergency vaccines are doing the job of helping governments to manage a pandemic that has overwhelmed national healthcare systems less equipped to serve the public after decades of privatisation policies (such as the UK’s NHS, for example).

Covid-19 has reset the balance of healthcare towards the public once more by putting the onus on each citizen to know how to stay well rather than to outsource the management of their own health after they fall sick.

Because not all Covid-19 cases will be symptomatic, this means the ability to self-test for an infection, and to know when to self-isolate and stay away from work or the mall even if one is asymptomatic or has mild symptoms. This is to minimise spreading the virus, especially to those who have existing health issues or comorbidities and may need to be hospitalised if infected.

This is the current approach towards managing the pandemic in Malaysia. As more people are vaccinated, it will be critical to monitor vaccine efficacy and if and how the virus is continuing to spread. This is done by using antibody tests, which are different from antigen tests. Here’s what you need to know about both.

What’s a Covid-19 antibody test?

Antibodies are produced by the body’s immune system in response to an invasion by a foreign substance such as a virus, bacteria or even a toxin.

So antibody tests were usually used to find out if a person had been infected by a virus or foreign substance some time in the past by testing for the presence of SARS CoV 2 antibodies in a blood sample.

Because Covid-19 emergency vaccinations are designed to prompt the body into producing antibodies to the SARS CoV 2 virus, antibody tests can also be used to find out if someone has been vaccinated.

So the presence of SARS CoV2 antibodies could mean a person was previously infected with the virus, or has been vaccinated.

Antibody tests can indicate how many people have recovered from Covid-19, including those who were asymptomatic. Antibody tests could also indicate who might have immunity, though more data and research are needed to find out how effective this immunity is against new variants of the virus and how long it lasts.

The effect of vaccinations can also be tracked by compiling data on the spread of the virus, geographically, chronologically and also across age groups, for example.

What’s a Covid-19 antigen test?

Foreign substances that invade the body such as the SARS CoV 2 virus are also known as antigens.

Antigen tests are done to detect the current presence of an antigen such as the SARS CoV 2 virus itself instead of antibodies to it (which your body may or may not yet have started to produce).

So, a Covid-19 antigen test is done to find out if you are currently infected.

What we still don’t know

As mentioned, more data is needed before we know whether SARS CoV 2 antibodies prevent reinfection and transmission to others, how long antibodies from the infection will last and how the immune system learns from previous infections to adapt to new ones.