What is serology/antibody test for COVID-19 and how will it work?

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A shortage of COVID-19 testing kits is a challenge currently faced by Australia and many other countries. A second type of testing, known as serology or antibody testing, may be the game changer in this chaos.

What is serology testing?

Instead of checking for the presence of COVID-19 virus itself, an antibody test will check if a person has detectable antibodies against the virus in their system. This is based on our understanding of how the immune system works. Antibodies are essentially immune system’s way to remember the fight with foreign pathogens. They make people who have had the infection resistant to being sick again with the same infectious disease.

Serology testing is already in use to check immunity to other vaccine-preventable diseases, including:

  • Chickenpox
  • Measles, mumps and rubella
  • Hepatitis
  • Diphtheria, pertussis, tetanus
  • Poliomyelities

Do we know that people won’t be infected twice?

There have been a few early reports that claimed people could develop COVID-19 twice. However, it is possible that those people had the resurgence of symptoms linked to the initial infection, rather than a second infection. A small study from China reported that COVID-19 virus could persist in the body for two weeks after the patients are considered “recovered”. In addition, preliminary research has shown that two monkeys did not contract COVID-19 for a second time.

Therefore, although it is not completely certain that people can’t be infected twice with COVID-19, it is likely the case.

How will serology testing help?

Serology tests should be cheaper to mass produce and easy to be completed at home, thereby massively alleviating the burden on our healthcare system.

For citizens and households, the serology test can inform people whether they are still susceptible to COVID-19. If yes, these people would benefit from social distancing and other preventative measures. However, if the results suggest that people have developed immunity to COVID-19, they do not need to isolate at home unnecessarily.

For researchers studying pandemic patterns of COVID-19, serology tests will provide data regarding how many people have been infected but showed no or mild symptoms. This will shed light on how the disease is spreading and how human immunity is evolving.

For healthcare providers and policy makers, large-scale serology test data can inform them which geographical areas have high or low proportions of susceptible individuals. Corresponding resources and travel restrictions can then be put in place or lifted.

In a hospital setting, serology test results among healthcare workers can also identify doctors or nurses who are safe to work in high-risk areas.

How far are we from serology tests?

Currently, labs and companies around the world are racing to develop these antibody tests. A few have already been used in small trials and commercialized, as can be found in this long list of diagnostic pipeline for COVID-19. However, large-scale data is still lacking. In the UK, Boris Johnson recently announced plans to buy antibody tests. In the US, the FDA has also given states authorities to engage with test development directly.

It appears that we are not far from mass production of antibody tests. However, even when the tests are validated, they will not replace the current test for COVID-19. The two would work in unison to make diagnosis more effective.