Should You Worry About Waning COVID-19 Antibodies?

In President Joe Biden's six-pronged plan to combat the spread of the Delta variant, booster shots are a prominent piece. Boosters are authorized for all three of the available COVID vaccines in the United States.

In addition to the previously authorized additional doses for moderately to severely immunocompromised individuals, the Centers for Disease Control and Prevention (CDC) now recommends a COVID-19 booster for everyone 5 years and older who:

• Completed the Pfizer or Moderna primary vaccine series at least five months prior.
• Received the Johnson & Johnson vaccine at least two months earlier.

But some scientists are asking if healthy Americans need booster shots. Continuing clinical trials show that antibodies from the Pfizer-BioNTech and Moderna vaccines slowly decline starting around six months.

Antibodies, however, are only part of the immune defense trained by natural immunity from COVID-19 infection or the vaccine.

Antibodies Are Only One Line of Defense

At a recent webinar hosted by the University of Southern California’s Annenberg Center for Health Journalism, Marion Pepper, PhD, an associate professor of immunology at the University of Washington, explained why she would personally refuse a booster shot as a healthy individual under the age of 65.

“What we’re seeing is that there are good immune memory cells that we can look at both their quality and their quantity,” Pepper said. “And more importantly, we are not seeing studies that are showing increases in disease. That’s what we have to look at with these vaccines: are they preventing disease? They are largely still doing that.”

Pepper explained that while antibody levels may gradually decline, they are not the only line of defense against infection and disease.

“What we need to remember is that antibodies are like a force field,” Pepper says. “If you’ve seen ‘The Incredibles,’ that is the force field that is sent out to protect the family. But if the infection gets past the antibodies, if there are holes in the force field, or that force field begins to wane, there’s still this whole team of superheroes underneath it.”

B and T Cells Work Behind the Scenes

The superheroes in this case are B cells and T cells, also known as the lymphocytes that make up part of the adaptive immune system.

When a vaccine is administered, whether it’s conventional or mRNA, the vaccine material communicates primarily with the B and T cells. It activates them to attack incoming viral or bacterial cells.

B cells are primarily responsible for producing antibodies. Still, even after that functionality wanes, they retain the memory of how to produce those antibodies in the event they encounter the same or similar pathogen in the future.

Pepper states that during the contraction phase of the body’s immune response, the body produces roughly 10% more immune cells, specifically B and T cells. While there may not be as many B cells over time, they retain the memory of producing antibodies so they can make them quickly when needed.

Even within the category of B cells, specialization occurs, creating plasma cells that produce antibodies for the person’s lifetime and memory B cells that patrol for viral cells.

So are there are as many antibodies? No. But if COVID-19 were detected, the memory B cells would ramp up antibody production and attack the virus in hours rather than days, lessening the severity of symptoms.

T-cells support the work of B cells and specialize as well. Some aid B cells in their functionality, while others directly attack infected cells. Between the two types of immune cells, they create an ongoing web of protection.

There’s a Reason for Waning Antibodies

As an HIV researcher, Monica Gandhi, MD, MPH, professor of medicine and associate division chief of the Division of HIV, Infectious Diseases, and Global Medicine at UCSF/San Francisco General Hospital, knows the importance of B and T cells.

HIV attacks T cells to destroy the immune system. At the webinar, she pointed out that there is a reason for decreased antibody production.

All three of the vaccines available in the U.S. code the body to produce the spike protein, and then the body produces a really strong immune defense by producing B and T cells, Gandhi explained. “Yes, the antibodies will wane because we don’t want our blood to be thick with all the antibodies to all the diseases we’ve ever seen in the world, but the B cells, with the help of the T cells, will ramp up those antibodies when needed.”

Antibodies should be produced on an as-needed basis. B and T cells help them do that.

So, even though antibodies are only one part of the immune equation, why have we placed so much emphasis on them? The answer lies in testing.

“It’s a lot easier to take blood and measure the antibody levels than it is to find and track these elusive, specialized cells,” Pepper said.

There is only one commercially available test for T cell analysis at the moment, making antibodies the most accessible yardstick for immune response.

Immunocompromised People Are the Exception

Giving boosters to immunocompromised patients ”makes sense,” Gandhi said. “We’ve always done that with immunocompromised patients [because] they may need a little more to build up their B cell and T cell memory.”

But outside of those with severe immunocompromised conditions such as cancer, HIV, or certain blood diseases, Gandhi emphasizes that the booster may just not be necessary.

All studies have shown consistent protection against severe disease, Gandhi adds. Even if an immunocompromised person encounters the virus, the likelihood of hospitalization is extremely low.

Since eradication is likely not on the table for the foreseeable future, scientists and the World Health Organization (WHO) are urging leaders to focus on initial vaccination for all people rather than booster shots for those already protected.

Correction: A previous version of this article stated there were no commercially available tests for T cell analysis. It was updated on September 20 to include the T-Detect COVID test.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.