Covid-19 antibody test in demand as people worry about immunity

Some people are undergoing a Covid-19 antibody test to determine if they are protected from the virus. Many health authorities and doctors want not to.

Antibody testing is one of the tools deployed by some people to help them decide which precautions to take to protect themselves and control the spread of Covid-19. Some vaccinated people want to know if their defenses are weakened and boosters are needed, while some previously infected people have the virus produced by the immune system. Some people want to measure the strength of the reaction.

41-year-old Katy Savage does not want to be vaccinated with the Covid-19 vaccine because she is worried about fetal side effects. She survived the August seizure, put on a ventilator for nine days, and believes that immunity from the infection is sufficient to protect her. The Center for Disease Control and Prevention recommends vaccination from August, citing studies showing that mothers or women planning to become pregnant are safe and effective during pregnancy.

She will be tested later this month to see if the antibodies are still circulating in her blood.

“For me, it’s OK, cool, I’m still fine. I’m still safe,” Savage said.

However, it is unclear what level of antibody will effectively prevent infection and severe cases of Covid-19, said Emily Volk, president of the American University of Pathologists. She said that getting a positive antibody test is not a substitute for getting vaccinated.

The CDC and the Food and Drug Administration do not recommend antibody testing to assess immunity after infection or vaccination. This is because testing cannot determine how much protection these antibodies can provide.

Studies have shown that there is a link between higher antibody levels and enhanced protection against Covid-19, especially for so-called neutralizing antibodies that prevent the virus from entering cells. Specific thresholds for the level of antibody that a person needs to protect from infections and severe illness are still determined by research.

“Whenever you order a clinical test, you usually have to keep in mind what you’re looking for,” Dr. Volk said. In the clinical context, it only causes confusion. “

The antibody test does not consider B cells that produce antibodies, or immune cells known as T cells that help identify the virus or kill virus-infected cells.

“Antibody testing does not give a complete picture of a person’s immune response to Covid,” said Eliza Seal, head of the Infectious Disease Serology Laboratory at May York Clinic in Rochester, Minnesota. I am.

The FDA has approved about 90 antibody tests, also known as serological tests, to search for proteins that fight Covid-19 that occur after infection or vaccination. Most tests require a blood draw and are analyzed in the laboratory. Some just need to be stabbed with a finger, while others use saliva samples.

Patients often have access to the test through a doctor or a company such as Laboratory Corp. of America, Quest Diagnostics, or CVS Health Corp. Costs range from $ 40 to $ 150 and may be covered by insurance. Wells Fargo & Co. According to the analysis, the amount of serological tests performed by Labcorp surged in August and September of this year, but not so much in Quest.

Antibody tests can be useful in some situations. Public health researchers use them to estimate which percentage of the population is infected with Covid-19. Immunologists and other professionals use them to study the immune response to Covid-19 after both infection and vaccination.

This test helps rule out whether certain symptoms of a child, such as abdominal pain or fever with dizziness, are caused by a condition called multisystem inflammatory syndrome that can develop after a Covid-19 infection. .. It also helps determine if someone was infected with Covid-19 if they were not tested for the virus when they were ill.

Antibody testing also benefits patients with immunodeficiency. Roberta Massaro, a former pharmacy inventory specialist in South Bend, Indiana, is taking a rejection inhibitor that suppresses the immune system by killing antibodies that could attack the transplanted liver that he received in 2013.

After receiving her second vaccination in April, she underwent an antibody test, indicating that she had Covid-19 antibodies in her system. “It was just for peace of mind,” said Massaro, who said he had taken precautions such as indoor masking, but resumed shopping at the supermarket during busy hours.

Some clinicians and pathologists have stated that antibody testing approximately one month after the second or third dose can help determine if immunocompromised patients responded to the vaccine. If not, some doctors warn those patients to act as if they were not vaccinated.

Allan Wells, director of medical care at the University of Pittsburgh Medical Center Clinical Research Institute, said:

However, Dr. Wells said checking antibody levels in patients other than these specific cases has little benefit so far. Antibodies usually peak shortly after infection and before they drop to baseline levels, so a decline in antibody response months after vaccination is not very clear about how well a person is protected. ..

For some viruses, including hepatitis B virus, scientists have identified levels of antibody prevalence corresponding to protective immunity. “Because Covid doesn’t have that yet, we rarely use the results explicitly at this time, except for public health laboratories and large-scale studies,” said Kelly Broblevsky, director of the Infectious Diseases Program. I am saying. Association of Public Health Research Institutes.

Another challenge is that not all tests look for the same antibody and results are not reported uniformly across different tests. Ligia Pinto, director of vaccines, immunity and cancer at the Frederick National Cancer Institute in Maryland, standardizes antibody test results for laboratories and researchers to make it easier to compare results among different scientists. Leading government support efforts to get it done. Study and get a better understanding of the data.

Defensive from Infections and Diseases To understand immune signals, researchers track specific parts of the immune response over time in a large cohort of patients and track them through breakthrough infections and reinfections. She said she needed to match the case with the disease.

“We’re doing very strong testing. We need to better understand what a particular level means,” Dr. Focus said.