A potential COVID-19 vaccine is shown at a clinic in London...

A potential COVID-19 vaccine is shown at a clinic in London on Aug. 5, 2020. Credit: AP/Kirsty Wigglesworth

When we think of the word "vaccine," we usually think of it in the singular, but there are really two types — active and passive. When it comes to COVID-19, the latter type may arrive quicker than you think.

Active vaccines are the kind we're all familiar with — the shots we get to inoculate us against polio, flu, etc. — and these are the type that are being developed as a safeguard against coronavirus by drugmakers including AstraZeneca, Moderna and Pfizer. They work by pushing the immune system, without causing an infection, to create antibodies in response to a virus or bacteria, which then helps prepare the body to successfully fend off a potential future infection.

Most of these vaccine treatments are the subject of large and lengthy trials, with approvals seen as months, rather than weeks, away. On Wednesday, Moderna's CEO said the company won't be able to apply for authorization of its leading vaccine candidate until at least late November because of the U.S. Food and Drug Administration's safety-data requirements, which are more rigorous for shots intended for large populations of healthy people. Passive vaccines, by contrast, are synthetic antibodies — an "immune system in a bottle" — that can be administered to both sick patients and those at risk from an infection to offer protection. It's these therapies that have come into focus lately.

Last month, Eli Lilly and Regeneron Pharmaceuticals each released positive data for COVID-19 antibody therapeutics they are developing as treatments and preventatives. Both companies are discussing their data with regulatory authorities, and there are reasons to believe their approval could come much quicker. Given their benign side effects, promising early data, and the FDA's controversial Emergency Use Authorization (EUA) for convalescent plasma, I would not be surprised to see either Lilly's or Regeneron's products get a similar green light, even if neither is really ready for prime-time use. This would help fulfill President Donald Trump's promise of a "vaccine" before November, if not the kind most of us understand him to mean. The question is, should they get this approval?

Lilly, in collaboration with AbCellera Biologics Inc. of Canada, is developing two different antibodies for COVID-19. One has reported some success, though Lilly's press release was scant on detail. While the therapy reduced viral load at the 2,800-milligram dose, it didn't at 7,000 milligrams, which is a bit odd. (In drug development, you always want to see a "dose response," i.e. the higher the dose, the greater the effect.) We don't know the details of the data and there may have been a trend, or most patients may have had a low viral load to start with.

Also, there was a 72% reduction in hospitalizations and emergency-room visits, which sounds great, but we don't know which dose drove that difference. And the data is based on very few patients, raising a risk that the effect was by chance. Lastly, the trial already found that 8% of those treated with the antibody had a mutation in the virus that made it resistant. This means that broader use of the therapy may result in the resistant variant taking hold in the population. So questions remain.

As for Regeneron, the company this week released an update on its progress, and while it defines its data as "descriptive," there are lot of parallels with Lilly's early read. Regeneron's treatment, a mix of two antibodies, reduced viral load, didn't really have a dose response (though its highest dose still worked) and appeared to reduce hospitalizations and ER visits. Also, being a drug cocktail, there is much less probability of the virus escaping through mutations.

Of note, much of the benefit of Regeneron's treatment was in people who had trouble generating an immune response to the virus. The finding could limit the use of the medicine; testing is barely keeping up with the pandemic, and the ability to rapidly identify potential high-risk patients may be challenging.

Taken together, though, these passive vaccines do seem to help sick patients, which suggests they may also work as prophylactics for those at risk of infection or serious disease. The data also bodes well for the potential success of an active vaccine. If artificially produced antibodies can fight the virus, those produced by vaccines could do the same.

As for whether either treatment deserves early approval, it's hard to say based on the information we have. Without seeing the full details of Lilly's trial or Regeneron's actual data rather than "descriptive" analysis, an approval would seem to be premature. So far, there's only proof of concept from the outpatient setting; regulators may want confirmation from continuing trials in the same group. But the FDA will have access to much more detailed data than is publicly available, which will aid in its decision. A "vaccine" by November, while a long shot, is technically not outside the realm of possibility.

Fazeli is Director of Research (DOR) at Bloomberg Industries and Senior pharmaceutical analyst.