Until now antigen tests had only gauged the presence of antibodies, not their quantity

The race to develop antibody tests has been as frenzied as the race to develop a vaccine – and there is symbiosis between the two. AP

A new crop of Covid-19 antibody tests is set to play an integral part in the development of an effective vaccine.

Siemens Healthineers is the first company to gain US Food and Drug Administration clearance for a test that assesses the quantity of long-lasting antibodies in the blood. Earlier antigen tests could only tell whether antibodies were present.

Swiss giant Roche is following up with its version.

Quantity over quality

The level of the body’s response is important in determining whether patients will develop immunity. It is also key to determining the effectiveness of vaccines as developers bring promising candidates through the sequential vaccine trials, documented here.

Moderna used a form of quantitative testing to show that all 45 participants in a Phase I trial of its experimental coronavirus vaccine developed antibodies. The company’s Phase III trial, however, was considerably larger — with about 30,000 people.

And that is one candidate out of a field of more than 160 different shots in development globally. This month, Russia announced its Sputnik V vaccine had been approved and was ready to be used.

The demand for quantitative antibody testing is set to grow and big diagnostics companies said they were ready.

“We’ve been talking to many of the vaccine companies and they’re very interested,” Thomas Schinecker, Roche’s head of diagnostics told Bloomberg in July.

Roche is in the final stages of development for its quantitative test and expected to share more information within months, the company said.

Quantitative antibody testing could also help with treatments involving convalescent plasma, in which people who have defeated Covid-19 donate their antibody-rich blood to those who are still fighting the virus.

“If five people showed up in a clinic, you can take blood and say, ‘Hey, this person has more antibody versus this other person and therefore is perhaps a better candidate for blood donation’,” said Deepak Nath, president of laboratory diagnostics at Healthineers.

Antibodies are not the body’s only defence against coronavirus – T cells can also kill virus-infected cells.

But antibodies are the easiest to measure, making the new quantitative tests a potentially powerful way to better grasp the immune system’s full response.

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