Researchers in Finland say they’ve created a novel nasal spray treatment that can provide brief but effective protection from the coronavirus and its many variants, including Omicron. In a recent preliminary study of cells in a petri dish as well as mice, the nasal spray appeared to block the virus from infecting cells up to eight hours following a dose. But more research would have to be done before we could expect this therapy to reach humans.

The experimental nasal spray is being developed by scientists at the University of Helsinki, and it relies on a slightly different approach of combatting the coronavirus than other methods.

“Its prophylactic use is meant to protect from SARS-CoV-2 infection,” study author Kalle Saksela told Gizmodo in an email. “However, it is not a vaccine, nor meant to be an alternative for vaccines, but rather to complement vaccination for providing additional protection for successfully vaccinated individuals in high-risk situations, and especially for immunocompromised persons—for example, those receiving immunosuppressive therapy.”

Vaccines work by training the immune system to recognize a germ without causing disease, which then allows us to produce our own natural supply of antibodies and immune cells specifically tuned to that germ if it appears in the future. We’ve also been able to mass-produce antibodies in the lab to the coronavirus, known as monoclonal antibodies, that can be given to people just after an exposure. The Helsinki team’s treatment, however, is a synthetic protein that’s much smaller than an antibody, but one that can still recognize and bind to the spike protein of the virus. To further amplify the protein’s potential, they smushed together three of them into a single package.

In theory, these antibody-like molecules can proactively inhibit any coronavirus they come into contact with from successfully infecting cells, for a short while at least. The ability to deliver the treatment as a nasal spray also means that these bodyguards can be sent directly into the upper respiratory tract, where most SARS-CoV-2 infections begin. Saksela, a virologist at University of Helsinki, is careful to note that the treatment isn’t intended to replace vaccines or other drugs.

In their research, released as a preprint late last month (meaning it has not been peer reviewed), Saksela and colleagues describe how they tested the spray on pseudoviruses made to look like various variants of the coronavirus, both as they tried to infect cells in a petri dish as well as in live mice.

Omicron has become a major problem largely because its many mutations allow it to partly evade recognition from the natural and lab-made antibodies created against the original strain of the coronavirus. But the team’s molecule apparently targets a region of the coronavirus spike protein that mutates very little. Ideally, this would mean that even Omicron couldn’t easily escape inhibition.

At least in the lab, that’s what Saksela and his team found. Whether it was Omicron, Delta, or the original SARS-CoV-2, the virus was stopped from infecting cells once even a modest dose of the spray was administered. And in mice exposed to the Beta variant of the virus, treated mice were much less likely to have any viral presence throughout their upper respiratory tract and lungs than a control group, with protection being apparent up to eight hours after a dose. The treatment also appeared to be safe and not associated with any noticeable harm.

Of course, this is all basic research that hasn’t yet gone through the full peer-review process. So while the results are definitely encouraging, time will have to tell whether their spray can work the same magic in humans. Should their work continue to show promise, though, Saksela thinks the spray would be valuable even after the pandemic phase of covid-19 has ended.

“This technology is cheap and highly manufacturable, and the inhibitor works equally well against all variants,” he said. “It works also against the now-extinct SARS virus, so it might well also serve as an emergency measure against possible new coronaviruses (SARS-CoV-3 and -4).”

Saksela doesn’t know how long it might take for the spray to reach clinical trials, and from there, to reach the market. He notes the spray could be considered either a drug or medical device, depending on a country’s regulatory process, which would further affect any timeline of development. But aside from continuing to work on a covid-19 treatment, the team might next try to develop a similar spray for other respiratory infections.