Antibodies Testing in Karachi Reveals COVID19 Exposure Runs in Double Digits
By Riaz Haq
CA
Antibodies testing of 7,000 adults in Karachi reveals that as many as 15% of them have already been exposed to COVID19 without experiencing symptoms, according to a study by Dr Wajiha Javed, an epidemiologist and head of public health and research at Getz Pharma in Pakistan.
It takes at least 40% of the population to be exposed to build herd immunity. This may be the only way to normalcy unless there is a vaccine available sooner.
Human Immune Response
Human body naturally produces antibodies to fight viruses of various kinds, including the coronavirus. Presence of antibodies in a person confirms that he or she has been exposed to a virus regardless of symptoms. It can even detect the body's immune response to a low-level viral load. Such an immune response also occurs to a vaccine which does not make you sick but helps build immunity. More low level exposure to viruses in large numbers of people is in fact a good thing because it helps build herd immunity. It takes at least 40% of the population to be exposed to build herd immunity. |
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Getz Study
Getz Pharma's Dr Wajiha Javed told me in the latest update on her ongoing work that serology tests have so far been administered to 7,000 adults aged 18-65 over the last 6 weeks in Karachi. 15% of them have tested positive for antibodies. People tested included those working for banks, restaurants, textile mills, factories, media and health care workers.
Antibody testing kits detect the response of the body rather than the virus or antigen itself. These tests do not have the issue of low viral load. Antibody tests can detect exposure to Covid-19 even in asymptomatic cases.
Generally, antibody testing kits have a high level of accuracy, especially on sequential testing. The kit Getz Pharma has been using has a sensitivity (the ability to correctly detect positive cases) of 95.3% and specificity (the ability to correctly detect negative cases) of 98.7% for IgG, and the sensitivity is 86.48% and specificity is 95.18% for IgM, according to Dr Wajiha Javed.
Asymptomatic Carriers
Over 90% of those who tested positive in Karachi did not have any symptoms or had only mild symptoms, Dr Wajiha Javed recently wrote in Dawn. But some were infectious and they were spreading the virus to others. Because of their non-existent or mild symptoms, they had not reached out to a PCR testing facility to get tested for Covid-19, and were only incidentally picked out for the antibody test during Getz's study.
Summary:As many as 15% of Karachi adults have been exposed to COVID19 with over 90% of them showing no symptoms, according to a Getz Pharma study in Pakistan. People tested included those working for banks, restaurants, textile mills, factories, media and health care workers. Human body naturally produces antibodies to fight viruses of various kinds, including the coronavirus. Presence of antibodies in a person confirms that he or she has been exposed to a virus regardless of symptoms. It can even detect the body's immune response to a low-level viral load. Such an immune response also occurs to a vaccine which does not make you sick but helps build immunity. More low level exposure to viruses in a large number of people is in fact a good thing because it helps build herd immunity. This may be the only way to normalcy unless there is a vaccine available sooner.
(Riaz Haq is a Silicon Valley-based Pakistani-American analyst and writer. He blogs at www.riazhaq.com )
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