Use Covid blood tests to calculate percentage of Thai population infected: virologist

MONDAY, MARCH 21, 2022

Leading virologist Dr Yong Poovorawan said that a blood test can detect Covid-19 infection even in people who have no symptoms from the disease.

Covid-19 infections behave like a pyramid, Yong said in a Facebook post on Monday. At the base of the pyramid are the 90 per cent or more of patients who have no or mild symptoms, especially with the Omicron variant.

However, at the top of the pyramid with severe symptoms are the elderly and people with underlying health conditions.

Yong cited a study of 80 children aged 5 to 11 who were not in a risk group and had never shown signs of infection. The study, conducted by the Yong-led Centre of Excellence in Clinical Virology, tested the children’s blood and found that five of them had been infected but remained asymptomatic as they developed natural immunity to the Covid virus spike protein. Such immunity cannot be produced by vaccines.

The children belong to a segment of the Thai population that remain asymptomatic and have to take blood tests to know they have been infected with Covid-19.

Thus blood tests would be the only way to find out how many people in Thailand have been infected with the virus and developed natural immunity.

However, natural immunity to the spike protein or nucleocapsid does not last long. The bodies’ immune response drops to 25 per cent one year after infection.

Yong said blood tests to detect natural immunity to the spike protein could be used in parallel with people’s vaccination history.

He added that Thailand should use blood tests to calculate what percentage of the population have been infected.