University of Minnesota studies antibodies for short-term immunity against COVID-19

Laboratory-made antibodies used by thousands of people as an experimental treatment for COVID-19 might also be a tool for preventing the pandemic's spread.

The University of Minnesota Medical School is one of more than 100 research centers enrolling patients in a study to see whether injections of the antibodies can fend off infections among household contacts of those who have tested positive for SARS-CoV-2, the virus that causes COVID-19.

Whereas vaccines enable patients to create their own antibodies against the virus, study participants receive injections of antibodies themselves, said Dr. Anne-Marie Leuck, an infectious disease specialist at the U.

"The advantage is that it's much faster ... because unlike traditional vaccines, it doesn't take weeks to work," Leuck said. "The downside is that the protection doesn't last as long. We don't know exactly how long it lasts — that's part of what this study will be looking at."

The concept is called "passive immunization," said Dr. William Petri, an infectious disease specialist at the University of Virginia School of Medicine. Doctors have used antibodies in this way for years, Petri said, so patients might benefit from temporary immunity against a number of ailments.

Patients bitten by a potentially rabid animal, for example, receive antibodies for near-term protection against developing rabies as well as a vaccine for long-term, active immunization.

"This use for COVID-19 is a variation on a theme — it's a well-established way of doing things," Petri said. "What passive immunization does in this case is, basically, it jump starts your immune system."

The statewide tally for people who have received at least one vaccine dose increased by 27,393 in the latest data release, for a total of 525,236 people so far. That's about 9.2% of the state's population — up from 6.7% on the previous Saturday, according to Star Tribune estimates.

The Health Department says 147,321 people have now completed the two-dose vaccine series, up from 105,361 one week earlier.

When former President Donald Trump got sick last year with COVID-19, he was treated with monoclonal antibodies like the ones now being studied for prevention. The laboratory-made product is designed to block the pandemic virus from attaching to and entering human cells.

Antibodies have been cleared for emergency use by federal regulators and are being made available to patients through a state-federal program.

Doctors initially feared that demand for the antibody treatment would far exceed the supply, but they've been surprised by the relative lack of patient interest thus far. While demand is slowly growing, the Health Department reported last week that only about 22% of the total doses accepted by the state have been used.

Participants are randomly assigned to receive either antibodies or a placebo, with patients and local research coordinators not knowing who is in each group. New York-based Regeneron, which manufactures the antibodies, sponsored the prevention study and announced preliminary results in January.

Researchers found 10 of 186 who received the antibodies were infected by SARS-CoV-2, the company said, compared with 23 infections among 223 people in the placebo group. Regeneron says that works out to a roughly 50% lower infection rate among those who received monoclonal antibodies.

None of the patients given antibodies came down with COVID-19 symptoms, whereas eight of those who received placebo developed symptomatic infections.

The company hopes to expand the study to about 3,000 patients overall with full data available during the second quarter.

"The data suggest that the antibody cocktail could provide this short-term immunity as a bridge to the active vaccine," a spokeswoman for Regeneron wrote in an e-mail to the Star Tribune. She added the antibodies might also "be an option for those who may be immunocompromised and not respond well to an active vaccine or are otherwise unable to be vaccinated."

The results thus far have been promising, she said, but they're also very preliminary. One challenge with the study is that researchers must quickly identify housemates of people who have tested positive and get them enrolled in the research within 96 hours.

"That's the hard part," Leuck said. "We need to get people in really quickly."

Using passive immunization could be an important way to protect caregivers for patients sick with COVID-19, Petri said. He thinks Regeneron might seek emergency use authorization (EUA) from the Food and Drug Administration to provide antibodies for prevention fairly soon.

"I don't know what the FDA is going to require of Regeneron," he said. "It would seem to me they are in a good position right now to apply for an EUA, so this can be used."

The Health Department reported Saturday that residents of long-term care and assisted-living facilities accounted for seven of the newly announced deaths and 3,966 fatalities since the start of the pandemic.

Seven-day averages for new cases have generally been declining over the past four weeks and have dropped considerably from November's peak for infections. At the same time, Minnesota has reported cases of new virus variants that are thought to spread more quickly.

Health Department figures on Saturday showed a total of 673,586 vaccine doses administered, up from last Saturday's count of 488,360 total doses.