On November 30, 2022, the Food and Drug Administration (FDA) deauthorized bebtelovimab for emergency use in the United States. This was the last monoclonal antibody drug authorized by the FDA to treat COVID-19. The decision was made because it is not expected to neutralize new Omicron subvariants.

Monoclonal antibodies are medications that can help your immune system fight against diseases. They can be given as infusions or injections, and they act like naturally made human antibodies that your body makes to fight infections or diseases, like cancer or autoimmune diseases.

Knowing more about these medications and their side effects can help you make informed decisions about whether to choose them as part of your treatments.

What is a monoclonal antibody?

A monoclonal antibody is a lab-made protein that can attach to targets in the body, like cancer cells or certain viruses.

There are many different types of monoclonal antibodies, and each one binds to only one kind of antigen, or foreign substance.

Monoclonal antibodies can be used by themselves or used to carry medication or radioactive substances to diseased cells.

Side effects can vary, depending on the specific monoclonal antibody being given and its intended target. Sometimes side effects can resemble an allergic reaction, especially the first time they’re given. Side effects may include:

Always talk with a healthcare professional about the possible side effects of the medications you’re taking, especially monoclonal antibodies. Each drug can pose different potential side effects, and being aware of the possibilities is important.

There’s currently little data on the long-term side effects of monoclonal antibodies. Most of the side effects are acute or injection-related.

COVID-19-specific reactions to monoclonal antibody treatment include:

  • It might interfere with your natural ability to fight off a future infection with SARS-CoV-2, the virus that causes COVID-19.
  • It might reduce your natural immune response to the COVID-19 vaccine.

As with any medication or treatment, there are potential side effects of monoclonal antibodies for COVID-19. Possible side effects of COVID-19 monoclonal antibodies can include:

It’s also important to remember that the monoclonal antibodies for COVID-19 haven’t been thoroughly studied with more serious side effects or long-term side effects, so there may be other adverse reactions that aren’t listed here. Talk with a healthcare professional about any concerns and questions you might have.

Most of the monoclonal antibodies cross the placenta, which brings up questions about their safety during pregnancy.

However, keeping various diseases stable during pregnancy, such as irritable bowel syndrome (IBS), is also important, and these medications have been used more and more during preconception, pregnancy, and postpartum. Each subspecialty of medicine has different guidelines about which drugs can or should be used during these periods.

Potential risks to the fetus should always be examined to determine whether treatment with these drugs should continue. The severity of the disease, as well as the specific drug, should be considered.

Side effects that have been noted include:

  • increased risk of infections for the infant in their first year of life
  • possible abnormal blood counts for the infant

More research needs to be done on the safety of monoclonal antibodies during pregnancy and any possible side effects. If you’re pregnant, talk with an an OB-GYN about the risks and benefits of continuing medication, the possible effects, and the available evidence.

Side effects of monoclonal antibodies are generally short-lived and typically go away within a few days.

If you notice any side effects that don’t resolve in a few days or get worse, let a healthcare professional know as soon as possible.

When to seek medical attention

Let a healthcare professional know immediately if you have symptoms of an allergic reaction, including:

Like any medication, monoclonal antibodies can have side effects. These side effects can include things like fever, nausea, muscle aches, and more. Side effects are usually mild and resolve after a few days, but long-term side effects aren’t known right now.

Talk with a healthcare professional about the possible risks and side effects of the monoclonal antibody that’s being prescribed to you. Each medication can pose different potential side effects, depending on the drug and what it’s treating, and they’ll be able to let you know what to look out for.