Earlier this week, the government organization authorized AstraZeneca's antibody cocktail, Evusheld, as a preventative COVID-19 treatment for certain populations.
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While recent COVID-related conversations have seemed to focus primarily on boosters (and new variants — hi, Omicron), over the past few days, the dialogue has shifted to center on a different topic: preventative treatments. And that's due largely in part to the fact that earlier this week, the Food and Drug Administration authorized the first monoclonal antibody treatment for the prevention of COVID-19 in certain populations.

On Wednesday, the FDA granted emergency use authorization for AstraZeneca's antibody cocktail, Evusheld, to be given to people ages 12 and older who are moderately to severely immunocompromised (e.g. those undergoing cancer treatment, taking immunosuppressing medications, or who've received an organ transplant) and, thus, may not mount an adequate immune response to viruses. (FYI, those with weakened immune systems are often unable to produce enough antibodies for ample protection after getting the vaccine.) The therapy is also an option for the rare individuals with a history of severe adverse reactions (e.g. anaphylaxis) to a COVID-19 vaccine or its ingredients, according to the FDA. Eligible recipients must also not be currently infected with the virus and cannot have been recently exposed to someone who's tested positive. (See more: Here's Everything You Need to Know About Coronavirus and Immune Deficiencies)

Until now, laboratory-produced antibodies (such as those in Evusheld) have been authorized only as early treatment of COVID-19 or as a preventative therapy for high-risk individuals immediately following close contact with someone who's infected. AstraZeneca's antibody cocktail, however, is intended to be used for pre-exposure prevention (PrEP) against coronavirus. At its most basic, PrEP essentially refers to a medication used to prevent the spread of disease (usually a virus) in people who have not yet been exposed to or infected by the said pathogen. "Pre-exposure prophylaxis (or PrEP) has traditionally been highly effective medicine taken to help an individual prevent getting HIV," explains Vivek Cherian, M.D., a Chicago-based internal medicine physician. "We're essentially talking about the same thing here, except now we're, of course, talking about a medication to help prevent a COVID infection."

One dose of Evusheld involves receiving two separate intramuscular injections — one for each monoclonal antibody (aka lab-produced molecules that act as substitute antibodies, according to the FDA) in the drug — in succession. By definition, monoclonal antibodies can restore, enhance, or mimic the immune system's attack on cells. In the case of COVID-19, in particular, these bad boys may block the virus that causes COVID-19 from attaching to cells, thereby making it more difficult for it to reproduce and wreak havoc, according to the FDA. They may also neutralize the virus, causing it to lose its ability to infect altogether.

Evusheld is engineered to be long-acting, which means the body metabolizes the treatment more slowly so that it can stay active for about half a year, according to The New York Times. This also means that recipients may very well have to receive a dose every six months.

How effective is Evusheld at preventing COVID? Great question. In a clinical trial involving participants older than 59 who are at higher risk for COVID-19, the cocktail was found to reduce the risk of developing a symptomatic infection by 83 percent, according to AstraZeneca. And while those findings sound pretty impressive, it's important to note that AstraZeneca has not broken out the results for those with immune problems specifically. What's more, it's still unclear how Evusheld stands up against the highly-mutated Omicron variant — but the company's scientists are currently running tests to hopefully figure that out, according to the NYT.

Still, with about 7 million Americans considered to be immunocompromised, the authorization of Evusheld as PrEP should allow for a sigh (or many) of relief. "This is extremely important to immunocompromised patients," says Dr. Cherian. "First of all, individuals who are immunocompromised carry a significantly higher risk of not only breakthrough infections with COVID but also a higher risk of severe disease and death." Plus, they're often unable to produce enough antibodies for adequate protection themselves when vaccinated, he adds. And for eligible recipients, the good news continues: Dr. Cherian estimates that, although no exact timeline has been announced, Evusheld "likely will be available in short order." After all, the U.S. government has already agreed to purchase 700,000 doses from AstraZeneca.

All that being said, it's especially important to understand that Evusheld is not a vaccine substitute — something that both the FDA and Dr. Cherian emphasize. Rather, it's meant "to help fill the gap that vaccines can't cover," he explains. "As far as impacting the overall fight against COVID-19, we need to still be utilizing our most important weapon against this virus: vaccines. If you haven't, get vaccinated, and if you're eligible, get a booster." (See more: Everyone Age 16+ In the U.S. Is Now Eligible for a COVID Booster Shot)

"What this therapy will do for the many immunocompromised patients out there — where vaccines likely have not been as effective — is finally give them hope to get past this pandemic, safely, healthy, and alive," says Dr. Cherian. And whether or not you're eligible for Evusheld, any (even slight) development toward protecting people against COVID-19 can provide likely everyone with some much-needed positivity.