Why Testing for Antibodies after COVID-19 Infection

On 31 December 2019, the World Health Organization (WHO) received the first case report about pneumonia of unknown cause in Wuhan, China1. Despite draconian containment measures such as lockdown and air travel bans in many countries, as of 4 June 2020, the COVID-19 pandemic has caused more than 6.6 million infections worldwide and the death toll has reached more than 380,000 globally. The numbers are still rising in countries such as Brasil, USA and Russia, and several countries like Bulgaria are seeing signs of the emergence of a 2nd wave.

Researchers around the globe have been investigating the virus that caused the pandemic, SARS-CoV-2. Analysis on the genomic data suggests that there are several strains of the virus: Type B virus is mainly found in East Asia, while type A and C are predominantly found in America and Europe, respectively2. Notably, the SARS-CoV-2 virus exhibits significantly higher binding affinity to the human angiotensin-converting enzyme 2 (ACE2) receptor, compared to the SARS-CoV virus which caused the SARS epidemic outbreak in 20023,4. This may explain why the SARS-CoV-2 virus is much more contagious. However, it is still unknown how such difference contributes to the outbreak of different strains in certain parts of the world.

To fight against the pandemic, companies have been developing virus detection kits, which can be roughly categorized into two groups: the first type of tests uses polymerase-chain-reaction (PCR) technology to directly detect virus genome from clinical samples such as nasal swabs. This group includes ID NOW COVID-19 assay, cobas SARS-CoV-2 test, and also a reliable CE-marked rapid COVID-19 test from Ender Diagnostics5, a newly incorporated Swiss diagnostics company. The other group is the serological assay for COVID-19 antibodies in bloodstream, indicating whether an individual developed possible immunity to the virus.  

In spite of the round-the-clock effort, effective vaccines and antiviral drugs still would take months, if not years, to be developed. So far, the most practical and effective ways to combat COVID-19 are washing hands, maintaining social distancing, wearing a mask (when social distancing is not feasible), and strengthening our health systems.

Most Frequently Asked Questions (FAQ):

1. What is the ratio of asymptomatic patients?

Recent research suggests a significant amount (25% to 80%) of COVID-19 infected patients are mild and asymptomatic6. These patients may even not be aware that they were infected. Thus, large scale antibody testing is crucial to inform about the actual infection rates.

2. Am I protected from the COVID-19 if I already have the antibody?

The antibody test is useful in determining whether you have contracted the virus in the past. It seems likely that contracting the virus can result in immunity as seen with other viruses. Nevertheless, it remains unknown how long the protective antibody lasts with this particular coronavirus. Currently, there is no evidence that people who have recovered from COVID-19 are protected from a second infection. In addition, patients who have not fully recovered could still be contagious, hence spreading the virus to people that they interact closely with, such as their families. 

3. Why do some children develop severe symptoms?

COVID-19-associated cases in children show multisystem inflammatory syndrome (MIS-C) which features are similar to Kawasaki disease. Unfortunately, it is not known what causes MIS-C and how it affects children. There is no vigorous evidence showing how MIS-C affects children who have underlying conditions. Children with MIS-C may develop a rash, stomach/muscle pain, fever (less common in children), bloodshot eyes, exhaustion, diarrhea, or vomiting. If a child shows any of these signs and symptoms, one should seek emergency care immediately. In a report7, about 23% of COVID-19-confirmed children have underlying conditions, such as chronic lung disease, cardiovascular disease, and immunosuppression. By 10 June 2020, children (under 20) account for about 3.5% of total COVID-19 cases in Switzerland8. In general, children with COVID-19 do not have severe symptoms. Nonetheless, parents should keep monitoring their children if they show the symptoms mentioned above. The best way to fight against COVID-19 is still to prevent contracting the disease, by washing hands and maintaining social distancing.

4. Is Remdesivir effective in the treatment of COVID-19?

There are no specific drugs approved by the Food and Drug Administration to treat COVID-19 patients. Gilead, a company producing the antiviral drug Remdesivir, is conducting two phase-3 clinical trials to evaluate the safety and efficacy of the drug in patients with severe and moderate symptoms, respectively.9 One of their recent reports10 suggests that patients who are treated with Remdesivir showed significantly shortened time to recovery, about 11 days on average, comparing to 15 days in the placebo group. The primary conclusion from this study is that Remdesivir is superior to placebo in treatment of hospitalized patients with COVID-19, shedding a light on its potential to expand the number of severe cases who could benefit from it. Similar results have been reported in another clinical trial in US.

5. Is there a vaccine for the coronavirus disease? How long does it take to develop a vaccine?

Currently there is no vaccine available for SARS-CoV-2. Typically, vaccine development can take several years. With current technology using egg- and cell-based platforms and working together with regulators, it can take five to six months to become available in the best scenario of H1N1 influenza-vaccine11. Currently, multiple platforms and technologies are under development for SARS-CoV-212, targeting the S-protein of the virus or the whole virion. However, the current novel pipeline and technologies for SARS-CoV-2 have not been thoroughly tested for safety and efficacy. The SARS-CoV-2 vaccine is under its way, calling for more patience.


1. https://www.who.int/csr/don/05-january-2020-pneumonia-of-unkown-cause-china/en/
2. Forster et al., 2020. PNAS. https://doi.org/10.1073/pnas.2004999117
3. Ou et al., 2020. bioRxiv. https://www.biorxiv.org/content/10.1101/2020.03.15.991844v4
4. Tai et al., 2020. Cellular & Molecular Immunology https://www.nature.com/articles/s41423-020-0400-4
5. https://enderdiagnostics.com/
6. https://www.healthline.com/health-news/50-percent-of-people-with-covid19-not-aware-have-virus
7. CDC COVID-19 Response Team: Stephanie Bialek et al., 2020. https://pubmed.ncbi.nlm.nih.gov/32271728/
8. https://covid-19-schweiz.bagapps.ch/fr-1.html
9. https://www.gilead.com/purpose/advancing-global-health/covid-19/remdesivir-clinical-trials
10. Beigel et al., 2020. The New England Journal of Medicine.https://www.nejm.org/doi/full/10.1056/NEJMoa2007764
11. https://www.who.int/csr/disease/swineflu/notes/h1n1_vaccine_20090806/en/
12. Fatima Amanat and Florian Krammer, 2020. Cell. https://pubmed.ncbi.nlm.nih.gov/32259480/

HEMEX supports the ender diagnostics team with clinical, regulatory and marketing services. HEMEX’s regulatory experts will support with the CE-certification of the test as an in vitro diagnostic medical device under the European In Vitro Diagnostic Regulation (IVDR). 

More Info: Dr. Xiao Yu

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