People with long Covid respond differently to vaccines: Study

New York, April 27 After people with long Covid received the Covid-19 vaccine, they produced antibodies against SARS-CoV-2 virus for months longer than expected, according to a study.

This suggests that long Covid might be caused by a dysfunction of the immune system, said researchers from the Smidt Heart Institute at Cedars-Sinai in Los Angeles.

The study was published in the journal BMC Infectious Diseases.

When a person has an infection, the immune system typically responds by making antibodies that block germs from entering cells.

Vaccines imitate an infection so that the body's immune system knows to release certain antibodies when it comes across a virus. In both cases, the immune system eventually stops creating antibodies when the suspected infection is gone.

"There's general consensus that some level of aberrant immune response happens in long Covid, and this study adds to the evidence to suggest this is true," said Catherine Le, from Cedars-Sinai.

To study the immune response of people with long Covid-19, the team analysed blood samples from 245 people diagnosed with long Covid and 86 people who had Covid and fully recovered.

All the study participants had received either one or two doses of a Covid-19 vaccine regimen.

"We examined one part of the immune system response, the production of antibodies, which is mediated by immune cells called B-cells," Le explained.

Specifically, the team looked at two types of antibodies that attack the virus that causes Covid-19.

One of these is called the spike protein antibody, which attacks a protein on the exterior of the virus. The other is the nucleocapsid antibody, which attacks the part of the virus that allows it to replicate.

The researchers found that people who were diagnosed with long Covid, produced higher levels of spike protein and nucleocapsid antibodies than people without long Covid.

Eight weeks after receiving a dose of the Covid vaccine, antibody levels in people without long Covid began to decrease, as was expected.

People with long Covid, however, continued to have elevated antibody levels, especially of nucleocapsid antibodies.

"What you would expect after getting a Covid-19 vaccination is a jump in your spike protein antibody levels, but you wouldn't expect a significant increase in nucleocapsid antibody levels," said Susan Cheng, from the Smidt Heart Institute.

"You would also expect these levels to eventually decrease and not persist for so long after vaccination."

Although this study shows that long Covid affects the immune system, it's too soon to draw firm conclusions from these findings, the researchers said.

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