Antibody Tests Get a Questionable Second Life...Regulators aren’t so sure.

[andhra_jp]

LabCorp, Quest Diagnostics suggest their tests help show a vaccine’s effectiveness. Regulators aren’t so sure. 

“While a positive antibody test result can be used to help identify people who may have had a prior SARS-CoV-2 infection, more research is needed in people who have received a COVID-19 vaccination,” the FDA said in a statement last month. The medical community shouldn’t rely on antibody tests as a means of assessing immunity to the virus, particularly after Covid-19 shots, the agency said.

The confusion extends beyond lab testing offered by U.S. companies. In India, the story of a man who said he had no antibodies after receiving his Covidshield jab went viral after it was picked up by the mainstream Indian press. He filed a complaint alleging he had been defrauded.  In the U.S. , the official Indiana state website says that people should test positive on an antibody test after they are vaccinated.

Commerical antibody tests were developed to measure recent infection from the virus, rather than the vaccine response. They can’t reliably establish whether a person is immune to Covid-19.  While they measure antibodies, protective proteins that vaccines produce by stimulating the body’s immune system, vaccines might also provide protection via other mechanisms,  like T cells. To make matters even more complicated, scientists don’t yet understand what amount of antibodies translates to protection from the coronavirus. Different tests, meanwhile, measure different aspects of infection that may not translate to the vaccine a person received.

Test-takers also must make sure the antibody test they plan on taking is the right type. Some tests, for example, measure antibodies against nucleocapsid protein, a specific structural part of the virus. But all of the vaccines approved in the U.S. elicit an immune response only to the virus’ spike protein, which would require a different type of test. A nucleocapsid antibody test might turn out positive if you’d contracted Covid, but not if you had only been vaccinated against it.

https://www.bloomberg.com/news/articles/2021-06-10/antibody-tests-get-a-questionable-second-life?srnd=prognosis