New AstraZeneca COVID Prevention Drug Will Not Replace Vaccines

An illustration of a red COVID virus particle surrounded by light blue monoclonal antibodies on a navy blue background.

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Key Takeaways

  • A newly-authorized monoclonal antibody called Evusheld may help prevent COVID-19 in people who cannot get vaccinated. 
  • However, the new treatment is not a substitute for vaccination for anyone who can safely get a vaccine.
  • Receiving an authorized or approved vaccine, as well as getting boosters when you’re eligible, is the best way to protect yourself against COVID.

AstraZeneca’s Evusheld is not the first monoclonal antibody treatment to earn authorization by the Food and Drug Administration (FDA) for use against COVID-19, but it is the first medication to be authorized specifically to prevent certain people from developing COVID in the first place.

The FDA said in December that Evusheld could reduce a person’s chance of developing COVID-19 by 77%. The early data also suggested that the treatment could be protective against the Omicron variant.

What Are Monoclonal Antibodies?

According to the FDA, “Monoclonal antibodies are laboratory-made proteins that mimic the immune system’s ability to fight off harmful pathogens such as viruses.”

However, experts want people to understand that a preventative treatment like Evusheld is not a substitute for vaccination in people who can safely receive one.

What Is Evusheld?

Evusheld is a combination of two monoclonal antibodies—tixagevimab and cilgavimab—that are designed to target the spike protein of the SARS-CoV-2 virus. This, in turn, blocks the virus from getting inside human cells. The drug is given as two injections, one right after the other.

Stuart Ray, MD, a professor of medicine at Johns Hopkins Medicine, told Verywell that the protection from a treatment like Evusheld is a type of “passive immunization” that is less durable than the protection that you get from vaccines.

Who Is Evusheld For?

The FDA’s authorization specifies that Evusheld is only for people who are not currently infected with COVID and who have not had recent close contact with someone who is infected.

In addition, Evusheld recipients must either:

How Does Evusheld Compare to Vaccination?

COVID vaccinations are safe and effective. Experts want to make sure that people understand that Evusheld, and other treatments like it, are not intended to replace a vaccine for most people.

“If you’re still not vaccinated against COVID-19, your best protection is to get the full vaccine dose and booster,” William Schaffner, MD, professor of medicine at the Vanderbilt University School of Medicine, told Verywell.

Monoclonal Antibodies vs. COVID Vaccines

Monoclonal antibodies can help prevent COVID if you’ve been exposed or help you avoid getting seriously ill if you’re infected because they give your immune system a boost.

Vaccines train your immune system and prepare it so that if you are exposed to the virus, your body will recognize it and know how to fight it off.

While monoclonal antibody treatments work as soon as you get them, they only last for weeks to months.

Protection from the vaccines kicks in after about 2 weeks from your last dose. While we’re not sure exactly how long each COVID vaccine will protect you, most keep working for at least several months, and boosters may offer even greater protection (and for longer).

Schaffner said that while Evusheld does supply antibodies to help protect against COVID, it must be given again every 6 months. On the other hand, the protection you get from the COVID vaccines may last longer.

Your body’s antibody response to protect you against COVID is crucial. Schaffner said the current vaccines also provide other important immune responses, including T cell and B cell activation, but Evusheld does not.

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.

What This Means For You

Evusheld is a new preventative COVID-19 treatment for people who cannot mount a sufficient immune response to COVID through vaccination alone or for whom taking the vaccine could be dangerous.

Like other monoclonal antibody treatments, experts want people to understand that Evusheld is not a substitute for vaccination in people who can safely receive one.

By Fran Kritz
Fran Kritz is a freelance healthcare reporter with a focus on consumer health and health policy. She is a former staff writer for Forbes Magazine and U.S. News and World Report.