What Are Monoclonal Antibodies? Doctors Explain the Popular COVID-19 Treatment
Monoclonal antibodies were approved as a COVID-19 treatment by the FDA last year, and again in February and May.
This therapy works best for people who face severe complications from SARS-CoV-2—but it must be administered soon after infection.
Monoclonal antibodies do not function as a replacement for the COVID-19 vaccines in the vast majority of people, experts say.
The three COVID-19 vaccines available in the United States have dominated the conversation for months, but there has also been a major development in the treatment of the disease: Last year (and again in February and May), monoclonal antibodies were approved as a therapy for patients at risk of developing severe disease. Lately, TV commercials have advertised the option for COVID-19 patients and the Biden administration has encouraged its use. But what are monoclonal antibodies, anyway?
These antibodies aren’t exactly the same as the ones your body produces from the vaccine—they’re created in a lab and focus on only the most dangerous part of the SARS-CoV-2 virus. But for those who are at risk of serious illness, plus people who cannot safely receive the vaccine, monoclonal antibodies can be lifesaving.
Here’s everything you need to know about monoclonal antibody treatment for COVID-19, according to experts—plus why you should still seek out the vaccines as soon as possible.
What are monoclonal antibodies?
Monoclonal antibodies are “laboratory-produced molecules that act as substitute antibodies that can restore, enhance, or mimic the immune system’s attack on cells,” according to the U.S. Food and Drug Administration (FDA). In this case, these antibodies replicate your body’s immune response to COVID-19, blocking or neutralizing the SARS-CoV-2 virus before it can make you severely ill.
Monoclonal antibody therapy is not new—in fact, it has been evolving for decades, explains Shmuel Shoham, M.D., an associate professor at Johns Hopkins University School of Medicine, and has been used for cancer patients. More recently, doctors have deployed the treatment for infectious diseases.
In November, the FDA authorized the monoclonal antibody treatments casirivimab and imdevimab, meant to be administered together to patients 12 and older who test positive for the virus and who are at high risk for progressing to severe COVID-19. Three months later, it authorized another pair, bamlanivimab and etesevimab, for the same population.
Another monoclonal antibody treatment, sotrovimab, was approved in May for the treatment of mild-to-moderate COVID-19 in patients above 12 who are at risk of severe COVID-19. “With the authorization of this monoclonal antibody treatment, we are providing another option to help keep high-risk patients with COVID-19 out of the hospital,” Patrizia Cavazzoni, M.D., director of the FDA’s Center for Drug Evaluation and Research, said in a press release.
Unlike the COVID-19 vaccines, monoclonal antibody therapy is administered after you’ve been diagnosed with the disease; the goal is to keep high-risk patients out of the ICU. It’s also not a sure thing—if you can get vaccinated, you should, since there’s no guarantee monoclonal antibodies will stop you from becoming severely ill.
How do monoclonal antibodies treat COVID-19?
When your body produces COVID-19 antibodies after contracting the disease or being vaccinated (these are called polyclonal antibodies), there isn’t a universal protective result; different types of antibodies focus on different parts of the virus’ structure. But lab-made antibodies only target the most crucial, destructive piece of the SARS-CoV-2 virus.
“The monoclonal antibodies focus on one part of the virus, which is called the spike protein,” Dr. Shoham explains. By jamming themselves between those spiky parts and your tissue, he says, monoclonal antibodies keep the virus from attaching to you so easily.
“[COVID-19] is caused by the virus itself, and then after a period of time, it’s caused by the body's overreaction to the virus,” Dr. Shoham continues. “For the monoclonal antibodies to work, they must [arrive] at the time the virus is causing the disease.” After about 10 days, there isn’t much for them to do. (That’s why any commercials you see focus on people who have recently been diagnosed with COVID-19, but are not yet severely ill.)
Monoclonal antibodies only provide protection for so long; the body cannot produce more of them. It’s still unclear how long protection lasts, but they’ll definitely have worn off after 90 days, the FDA notes.
Are monoclonal antibodies safe?
“Anything that you put in your body can have side effects,” Dr. Shoham says. “Complications with monoclonal antibody infusions are pretty uncommon, but some people can have an allergic reaction to it,” much like the COVID-19 vaccines. Other minor complications include fever, rash, nausea, chills, and feeling lightheaded.
In clinical trials, a single infusion of bamlanivimab and etesevimab “significantly reduced COVID-19-related hospitalization and death” compared to a placebo over the course of a month, the FDA explains.
Who should receive monoclonal antibodies?
Monoclonal antibody therapy has been authorized by the FDA in COVID-19 patients 12 and older who are at high risk for developing severe disease. “The first two days [after diagnosis] are the best time to get it,” Dr. Shoham explains.
This treatment is also ideal for those who must approach the COVID-19 vaccines with caution, including immunocompromised people, those who are receiving high doses of steroids, transplant patients, and people with certain cancers. “They should still get the vaccine, but their response to the vaccine might not be as robust,” Dr. Shoham says. “Therefore, they may not be as protected.”
Monoclonal antibodies are not FDA-authorized for hospitalized COVID-19 patients or those who are receiving oxygen, because they won’t be able to help much. Plus, the FDA notes, monoclonal antibodies could be associated with “worse clinical outcomes” for patients who require high-flow oxygen or ventilation.
“If somebody is already in the intensive care unit or in the hospital on oxygen, the disease is mostly not caused by the virus anymore—it’s caused by the body’s overreaction,” Dr. Shoham says. In that case, the antibody treatment won’t be effective.
Can monoclonal antibodies replace the COVID-19 vaccine?
No, at least not in the long term. There are two types of immunization, Dr. Shoham explains: active immunization (from either a vaccine or the virus itself) and passive immunization (from therapies like monoclonal antibodies).
Active immunization teaches the body to produce antibodies, does not take effect immediately, and lasts a relatively long time; passive immunization provides pre-made antibodies, does not teach the immune system to make more, takes effect almost instantly, and lasts a relatively short time.
Another key difference is related to transmission. The COVID-19 vaccines appear to make asymptomatic transmission less likely, but monoclonal antibodies do not limit a patient’s ability to spread the disease.
The Centers for Disease Control and Prevention (CDC) currently recommends that anyone who received monoclonal antibody therapy wait at least 90 days after COVID-19 diagnosis to receive the available vaccines. This is a precautionary measure to “avoid potential interference of the antibody therapy with vaccine-induced immune responses,” the agency explains.
Vaccinated people who become infected (known as “breakthrough” cases), however, should still consider monoclonal antibody treatment if they fall into the FDA-approved categories, the CDC explains, with no concern for timing. “Unless someone has a specific reason not to get the vaccine, and those are very rare, the vaccine is something that I would strongly encourage,” Dr. Shoham says.
This article is accurate as of press time. However, as the COVID-19 pandemic rapidly evolves and the scientific community’s understanding of the novel coronavirus develops, some of the information may have changed since it was last updated. While we aim to keep all of our stories up to date, please visit online resources provided by the CDC, WHO, and your local public health department to stay informed on the latest news. Always talk to your doctor for professional medical advice.
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