A negative antibody test does not mean the Covid-19 vaccine did not work

“Many people will test negative on the antibody test, and that does not mean the vaccine didn’t work.” …

One man in India is worried that his Covid-19 vaccine shot may not be working.

Pratap Chandra, a resident of Lucknow in Uttar Pradesh, got himself tested for antibodies against Covid, 28 days after receiving the Covishield jab. After the test concluded that he had no antibodies against the viral infection, he concluded that the vaccine maker and India’s health ministry were to blame.

Covishield, the AstraZeneca vaccine manufactured by the Serum Institute of India, is the dominant vaccine in the country’s ongoing immunisation programme. So far, a majority of the 216 million doses administered in India have been of Covishield.

The course of the law is yet to be determined, but Chandra’s complaint itself may be based on shaky scientific evidence. Antibody tests, experts say, do not tell you whether a vaccine works or not.

For one, the antibody tests can detect if you had an infection in the past because of the type of antibodies it tests. A vaccine, on the other hand, induces a complex variety of antibodies that may not be detectable in a rapid test.

“After the vaccines, a lot [of] people are going to get antibody testing—‘Oh, I want to see if it’s working.’ It actually has very little correlation,” Rob Murphy, executive director of the Institute for Global Health and a professor of medicine and biomedical engineering at Northwestern University, told The Washington Post in February. “Many people will test negative on the antibody test, and that does not mean the vaccine didn’t work,” he added.

For this reason, the US’s Centers for Disease Control and Prevention (CDC) recommends against the use of antibody tests after vaccination because those that test for specific antibodies—and their correlation to each other—can identify a vaccine immune response. These tests, for instance, do not identify a more complex cellular response, which may play a role in vaccine-induced immunity, according to the CDC.

“A vaccinated person should not be alarmed or worried if they receive a negative antibody test result because this test does not detect antibodies from the Pfizer, Moderna, and Johnson & Johnson’s Janssen COVID-19 vaccines, which were developed against the spike protein of the virus,” said Fernando Martinez, medical director of laboratory medicine at the MD Anderson Cancer Center in Texas. Vaccines like Covishield also use the spike protein of coronavirus, encoded into the DNA of an adenovirus, to guide cells to create specific antibodies against the disease.

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