Antibody Drugs Could Act as a Temporary Covid-19 Vaccine

Results from clinical trials show promising signs

Emily Mullin
Medium Coronavirus Blog
4 min readJan 28, 2021


Photo: Boston Globe/Getty Images

Lab-made antibodies are showing promise for preventing Covid-19 infection in those at high risk of contracting the disease. With vaccines in short supply in the United States and elsewhere, the drugs could be used to provide short-term protection until people can get vaccinated.

The good news came in quick succession over the past week from pharmaceutical giant Eli Lilly and biotech firm Regeneron Pharmaceuticals. First, Eli Lilly announced on January 21 that its antibody drug bamlanivimab prevented Covid-19 cases in nursing homes.

The company retrofitted RVs into mobile research labs capable of preparing the drug and parked the trailers at nursing homes. That way, when Covid-19 cases started cropping up at facilities, investigators could be ready to quickly deliver the drug, which is given via IV drip. In results publicized last week, Eli Lilly found that the drug reduced symptomatic infections among nursing home residents by 80% compared to those who got a placebo. Among staff members, there was a 60% reduction in cases. The trial included 965 people — 299 residents and 666 staff members.

Regeneron followed up on January 26 with the announcement that its cocktail of two lab-made antibodies also prevented infection in people living with someone with Covid-19. In an initial analysis of 409 people in an ongoing clinical trial, the drug reduced infections by about 50%. Ten people among 186 who received the drug ended up getting Covid-19 compared to 23 people out of 223 people who got a placebo.

The drug also seemed to reduce the length of sickness in people who got Covid-19. Symptoms lasted a week or less for those who received the antibody cocktail, while 40% of people in the placebo group had infections lasting three to four weeks. Infected people in the placebo group also had much higher viral loads than those who got the drug.

In contrast to Eli Lilly’s treatment, Regeneron’s drug was formulated so that it could be given as an injection, which makes it much more convenient for health care workers to administer.

Known as monoclonal antibodies, both companies’ drugs mimic natural antibodies that the immune system makes to fight off the coronavirus. When a person is exposed to a virus or other pathogen, the immune system starts pumping out antibodies in response. Some of these antibodies are particularly potent. Finding these antibodies, however, is often like searching for a needle in a haystack. Scientists look for them in patient blood samples, mice, or even llamas, then isolate the antibodies and test their ability to neutralize the virus in the lab. Synthetic versions of the human antibody are then brewed in large steel vats. You can read more about the process in this story I wrote for OneZero last May.

Both the Eli Lilly and Regeneron drugs were authorized for emergency use by the U.S. Food and Drug Administration in November for treating people with mild or moderate Covid-19 who are at risk of progressing to serious disease. This new data suggests the drugs could also be used to prevent infections in at-risk people who haven’t been vaccinated yet. Scientists estimate that protection from monoclonal antibodies lasts about a month.

Even as Covid-19 vaccines are becoming available and being distributed around the United States, hundreds of thousands of people across the country continue to be infected daily. Those who get sick tend to spread the infection to household members and other close contacts.

“[Our] antibody cocktail may be able to help break this chain by providing immediate passive immunity to those at high risk of infection, in contrast to active vaccines which take weeks to provide protection,” said George Yancopoulos, MD, PhD, president and chief scientific officer at Regeneron, in a company statement.

Regeneron and Eli Lilly’s findings have not yet been peer reviewed or published in an academic journal. Both companies announced their results in a press release.

And despite the promise of antibody drugs, getting them to people who could benefit from them remains a challenge. While more than 640,000 doses of the drugs had been shipped to hospitals and other health care providers by January 6, only about a quarter have been used this month, according to a story this week by the Philadelphia Inquirer. If the country’s testing debacle and slower than expected vaccine rollout has taught us anything, it’s that logistics plays a crucial role in saving lives during a pandemic.



Emily Mullin
Medium Coronavirus Blog

Former staff writer at Medium, where I covered biotech, genetics, and Covid-19 for OneZero, Future Human, Elemental, and the Coronavirus Blog.