Covid-19 Antibodies

In an infection, the body mounts an immune response. One of the ways is by the production of antibodies or immunoglobulins (Igs). There are five kinds of immunoglobulins or Igs: G, A, M, D, and E. 

IgM and IgG are tested for Covid-19. The IgM usually shows up first, followed by the IgG. COVID-19 antibody testing tests for both. The COVID-19 nasal swabs tests for the SARS-CoV-2 RNA. SARS-CoV-2 causes COVID-19.  

This article from two studies. A preprint study from Chongqing, China, reviewed the charts of 221 patients and a paper published in Oxford Academic from Shenzhen, China, that studied 173 patients from the time they got admitted to the hospital. 

The studies monitored the nasal swabs and the presence of IgM and IgG in the blood. The nasal swabs and antibodies were repeatedly tested in the two studies during the patients’ hospital stay.

RNA stands for ribonucleic acid. The nasal swab test for COVID-19 looks for the viral RNA.

Antibody levels

In the Chongqing study, the IgM and IgG antibodies peaked 19-21 days after the symptom onset. 

The Shenzhen study took 15-39 days after the onset of symptoms for 100.0% of both IgM and IgG to become positive.

Not all patients develop antibodies. 2 patients in the Chongqing study did not develop antibodies during the whole course of the disease. 

Both studies report that a higher IgG is associated with worse clinical outcomes. 

The conclusions of both studies.

1. Antibody testing can be used together with the nasal swab to diagnose Covid-10, where the nasal swab may be negative.
2. A high antibody level during the acute or hospital phase is associated with worse clinical outcomes. Based on this, the authors warned that recovered patients’ antibodies might cause organ deterioration if given to sick patients. Thus, more studies are needed. [1]
3. A negative antibody test does not rule out the absence of Covid-19. 
4. Antibody testing can be used as a guide for deciding when to discharge a patient from the hospital. 

Does an antibody to COVID-19 provide immunity?

We don’t know. People who had SARS or Severe Acute Respiratory Syndrome in 2002-2003 had two years of immunity. 86% (6/7 people) of those with Middle Eastern Respiratory Syndrome or MERS had antibodies for 34 months.

COVID-19 has only been around since December 2019, and more studies need to be done to know if the antibodies are protective and for how long. The other question is, will the antibodies protect against the mutations of the SARS-CoV-2 virus.  

The knowledge about Covid-19 is rapidly evolving. Information may update as new researches are done. Stay current by subscribing.

Don’t Get Sick!

References:

Zhao et al. Antibody responses to SARS-CoV-2 in patients of novel coronavirus disease 2019., Clinical Infectious Diseases, ciaa344, https://doi.org/10.1093/cid/ciaa34