Watch: Two types of Covid-19 tests explained

Dr Kerrigan McCarthy, senior pathologist at the National Institute for Communicable Diseases (NICD), has outlined the two types of Covid-19 tests which are currently available in South Africa.

McCarthy said that the ‘antibody’ test looks for an antibody response while the second test looks for the virus itself.

She noted that antibodies are commonly measured in blood while the virus is checked for using throat swabs.

“One of the problems with antibodies is that they are only formed on days 7-10 post-infection. This is slightly longer than when one takes a throat swab and the swab is shown as positive.

“In other words, the first test to become positive will be the throat swab and not the antibodies. The problem is that one may take a blood test for antibodies, it may show as negative, but the throat swab is already positive.

“So the rapid blood tests – which are usually based on antibody detection – is not an ideal test for Covid-19.”

McCarthy said that researchers were now looking for the throat swab test to be done quicker.

She said that the GeneXpert test which is used for TB can accomplish the same results as a throat swab in a shorter amount of time.

However, McCarthy noted that there are challenges in using this test as it requires the use of a specific cartridge produced by a company in the US which is only releasing 10% of its production line globally.


As of Wednesday (24 June), a total of 1.416 million tests have been conducted in South Africa, with 34,122 tests conducted over the past 24 hours.

Government’s data shows that these tests are fairly evenly split between the government and private sector, with 703,517 private and 713,377 public tests conducted to date.

There are now 111,796 total cases of coronavirus in South Africa. This is an increase of 5,688 cases from 106,108 cases reported on Tuesday, and a new 24-hour record.

The country also reported 103 new Covid-19 related deaths, taking the total up to 2,205, and a mortality rate of 2%, while recoveries increased to 56,874, which translates to a recovery rate of 50.9%.

Vaccine trial 

On Tuesday (23 June), University of the Witwatersrand (Wits) vaccinology professor Shabir Madhi announced the start of the first clinical trials for a Covid-19 vaccine in South Africa.

Madhi said that Wits is collaborating with the University of Oxford to begin vaccinating South Africans and determine the efficacy of the Ox1Cov-19 vaccine in the country.

“This is a landmark moment for South Africa and Africa at this stage of the Covid-19 pandemic,” Madhi said.

“As we enter winter in South Africa and pressure increases on public hospitals, now more than ever we need a vaccine to prevent infection by Covid-19.”

“We began screening participants for the South African Oxford 1 Covid-19 vaccine trial last week and the first participants will be vaccinated this week,” he said.

The South African vaccine trial has been subject to rigorous review, the university said, and it has been approved by the South African Health Products Regulatory Authority (SAHPRA) and the Human Research Ethics Committee of the University of the Witwatersrand.

The vaccine is already being evaluated in a large clinical trial in the UK where more than 4,000 participants have already been enrolled.

In addition to the South African study, similar studies are about to start in Brazil and the United States.


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Watch: Two types of Covid-19 tests explained