No Need for a Test to See if the COVID-19 Vaccination is Working, Northwestern Infectious Disease Experts Say

No Need for a Test to See if the COVID-19 Vaccination is Working, Northwestern Infectious Disease Experts Say

By Howard Wolinsky

Robert Murphy, MD, an infectious disease expert at Northwestern University in Chicago, said that on a nearly daily basis vaccinated patients ask whether they should undergo a test to see if the vaccine took.

“People are asking me all the time. People are nervous.  Some people want to know whether the vaccine worked on them or not,” said Murphy,professor of infectious diseases at Northwestern University’s Feinberg School of Medicine and executive director of the Institute for Global Health.

He said the people who ask for such tests typically have an underlying condition, such as cancer, rheumatoid arthritis, lupus erythematosus and other conditions where their immune systems are compromised by the disease itself or by treatment with medications, such as steroids.  Most of these patients were excluded from the clinical studies which led to vaccine approval.

The COVID-19 vaccines all produce a specific antibody, he said.  Unfortunately, no commercial tests are available yet for this purpose though some laboratory tests might be useful, noted Murphy, one of the founders of  Northwestern COVID-19 Vaccine Communication and Evaluation Network (CoVAXCEN).

The coalition, headquartered in the Institute for Global Health's Center for Global Communicable and Emerging Infectious Diseases with the cooperation of the Center for Communication and Health convenes a panel of experts in immunology, infectious disease, epidemiology, regulatory science, and health communication to develop and share information on COVID-19 vaccines.

Murphy said another group of otherwise healthy patients asks about post-vaccination testing. These include patients who just want to confirm that the COVID-19 vaccine is triggering protective antibodies.

The infectious disease expert said existing commercial antibody tests are based on antibodies from patients who had COVID-19 infections as opposed to COVID-19 vaccines.

“The antibodies are different,” he said. “You may have a commercial test today but it won’t necessarily detect the antibodies from the vaccine, and the vaccine still works in 90-95% of recipients. It’s not as simple as ‘I’m going to get the antibody test to find out if the vaccine worked.’”

Babafemi Taiwo, MBBS, Chief of Infectious Diseases in the Department of Medicine at Northwestern Medicine, stressed that some commercially available blood tests that identify antibodies to the spike protein of SARS-CoV-2 can be positive after vaccination since many vaccines target this spike protein. These antibody tests are different from tests that directly identify the virus (direct viral tests), such as from nose or throat swabs. The direct viral tests cannot be affected by vaccination, he said.

The infectious disease expert, who is a member of CoVAXCEN, added that scientists are still learning about how well positive antibody tests correlate with immunity, so the priority now needs to be getting the population immunized rather than worrying about post-vaccination testing.

 “Our efforts now are about vaccinating and protecting the public,” Taiwo said. “If somebody is vaccinated, the idea is that the vaccine will induce an immune response.”

He said while some people may seek antibody testing to understand whether they are protected after vaccination, antibodies alone are an incomplete measure of immune responses.

“The vaccines can trigger different aspects of the immune system,” Taiwo said.

For example, he said the response of some specific “fighter cells,” or T cells, a type of white blood cells, may provide important information about immune responses to the vaccine.

But he said measuring T-cell responses poses logistical issues because it requires drawing large quantities of blood and the tests themselves are relatively complicated to perform.

“We also do not have enough understanding of the immune response of T cells in the context of COVID and there are no commercially available tests for this,” he said.

Taiwo said, “We rarely routinely test T cells clinically (except in persons with HIV or other causes of weak immune systems) even though we’ve known for decades that it’s extremely important. When somebody goes to the hospital we don’t routinely say, let’s take the T cells to see how they’re responding to this or that. We will say, let’s see your blood and we’ll check for antibodies or antigens. Those are easy targets that we can reach. There is no commercially available way to quantify the T-cell response to COVID vaccine now.”

Another angle on post-vaccine testing relates to the question of how long does immunity last with these vaccines.

These are the early days. Pfizer-BioNTech and Moderna, major vaccine makers, have reported that the antibodies elicited by their vaccines persist for at least six months. The vaccine manufacturers are committed to keep testing the study volunteers for at least two years to see how long the antibodies last.

“We don’t know how long the vaccine is going to work. We don’t know if the vaccine’s antibodies and immunity that you get from the vaccine are going to work against all the variants that may pop up,” Murphy said.

The vaccines will differ in how well they protect against different strains. For example, there is a new report suggesting that the AstraZeneca vaccine is quite weak against the South African variant.

Murphy said vaccines, authorized for emergency use by the U.S. Food and Drug Administration, protect against the B.1.1.7, or the UK variant, which is becoming dominant in the U.S, but it’s possible that the vaccines will not protect against future variants.

He noted that immunity status does change over time. A good example is the influenza virus, which changes every year.

“The thing with the flu is, the antibodies don’t go away, but the flu changes every year. You have to get a new set of antibodies, a new immunity,” he said.

Hence, new flu vaccines are needed every year, and that may be the scenario that applies for COVID-19. All the vaccine makers are exploring the idea of combining COVID-19 boosters protecting against new variants with influenza vaccines.

What can patients do if someday effective antibody testing becomes available and shows they have lost protection?

Murphy said there is no answer yet to that question. Some people may never develop the antibody, yet they are protected. He said research is needed to determine if such patients might benefit from booster shots of the vaccine they have taken or immunizations from other vaccines.

CoVAXCEN member Alessandro Sette, PhD, an immunologist at the Center for Emerging Diseases at the La Jolla Institute for Immunology, is working on other biomarkers confirming vaccine protection. CoVAXCEN member Thomas McDade, a biological anthropologist at the Institute for Policy Research and Feinberg School of Medicine, Northwestern University, also is developing testing to follow the immune response in his SCAN study of 9,000 patients in Chicago.

Headquartered in the Institute for Global Health's Center for Global Communicable and Emerging Infectious Diseases with the cooperation of the Center for Communication and Health, we seek to achieve consensus on a variety of issues related to the safety and efficacy of COVID-19 vaccines and then produce and disseminate written materials for scientists, healthcare professionals, and the general public describing its conclusions.

Northwestern COVID-19 Vaccine Communication and Evaluation Network (CoVAXCEN)  seeks to achieve consensus on a variety of issues related to the safety and efficacy of COVID-19 vaccines and then produce and disseminate written materials for scientists, healthcare professionals, and the general public describing its conclusions.

Howard Wolinsky is a Chicago-based freelance medical writer and author. He is the former medical reporter for the Chicago Sun-Times. He has won awards for medical writing from the American Public Health Association, the American Bar Association, the Association of Health Care Journalists, and the Chicago Headline Club’s Peter Lisagor Award (“the Chicago Pulitzer''). The Sun-Times twice nominated him for the Pulitzer Prize.