Exposure to COVID-19 May not Quarantee Immunity for Asymptomatic Coronavirus Patients?

COVID-19 remains the biggest news item of 2020. Across the
world, the number of people infected continued to rise. Nearly half a million people have died from the disease, since it first sprang up in December 2019.
Scientists are frantically trying to study and understand
the nature of the novel coronavirus. One of the main areas of focus concerns how human immunity responds to the virus and whether those who have been exposed to it and recovered can be considered resistant to COVID-19.

COVID-19 New Study

According to a new study published in Nature Medicine, the
levels of antibodies in asymptomatic patients tend to drop significantly two
months after discharge from the hospital. It is not clear if that means the
subjects can be re-infected. However, it points out the need to study long-term immunity due to the development of antibodies.
COVID-19 is caused by coronavirus
Coronavirus has spread to all regions of the world
The subjects of the research were 37 asymptomatic COVID-19
patients in Wanzhou District, China. The control group was composed of 37 symptomatic individuals of the same age and sex. After detecting the asymptomatic cases through contact tracing, the researchers had them quarantined until they were COVID-19-free. They then tracked all the subjects for eight weeks after discharge from either the quarantine centers or hospital.

COVID-19 Antibodies

By design, the researchers measured two types of antibodies –
neutralizing antibodies and immunoglobulin G (IgG). They found significant
drops in blood levels of IgG for both the asymptomatic and symptomatic cases over eight weeks after being discharged from the hospital. In asymptomatic cases, IgG levels dropped by 71.1 percent while that of symptomatic cases dropped by 76.2 percent.
More significantly, asymptomatic cases had lower levels of
IgG than their symptomatic counterparts at all the phases of COVID-19. By the eighth week, 40 percent of the asymptomatic cases had no traces of IgG in their blood.

Symptomatic Cases

Even though neutralizing antibodies dropped in both the
asymptomatic and symptomatic cases, there was a significant amount at week eight. While asymptomatic cases have neutralizing antibodies drop by 8.3 percent, their symptomatic counterparts had a drop of up to 11.7 percent.
However, it is not clear if the data indicates the possibility of re-infection with COVID-19 months after developing antibodies. London-based scientist Liam Smeeth says there is need for large-scale and long-term studies to inform policies to do with social distancing.


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