An over-the-counter nasal spray widely used to treat seasonal allergies could help prevent COVID-19 infections, according to results from a clinical trial released Tuesday.
The antihistamine azelastine, available in spray form, has shown antiviral activity in a growing number of studies against several respiratory viruses, including influenza, RSV, and the virus that causes COVID-19, reports NBC News.
German researchers at Saarland University Hospital enrolled 450 adults, mostly in their early 30s, to test azelastine’s effectiveness. One group of 227 participants received a puff of the nasal spray in each nostril three times a day, while the other 223 used a placebo spray.
Over nearly two months, all participants took rapid COVID-19 tests twice a week. By the end, the incidence of infections was 2.2% in the azelastine group compared with 6.7% in the placebo group, the study published in JAMA Internal Medicine found.
The spray also appeared to lower rates of other symptomatic respiratory illnesses. Researchers suggested azelastine may bind to the virus in the nasal mucosa — the moist lining of the nose where pathogens enter the body — and inhibit a key enzyme used for replication. Another theory is that the drug interacts with the ACE2 receptor, the main entry point for the COVID-19 virus into human cells, preventing infection.
Dr. Robert Bals, professor of internal medicine and pneumology at Saarland University and senior author of the study, said the findings indicate the spray could serve as a preventative against COVID-19, “especially when community transmission is elevated or in high-risk settings such as crowded indoor events or traveling.”
Bals emphasized that the trial had limitations, including that participants were young and generally healthy. He cautioned that azelastine should not be viewed as a substitute for vaccination and said larger studies are needed before recommending routine use, particularly for older adults or people with weakened immune systems.
Dr. William Messer, associate professor of molecular microbiology and immunology at Oregon Health & Science University, who was not involved in the trial, called the results “reasonably convincing” but questioned compliance with the frequent dosing schedule.
The mask may be more awkward and annoying, but might be easier to comply with than remembering a thrice-daily nasal spray day after day, Messer said.
Other experts said more evidence is needed in high-risk groups. Dr. Peter Chin-Hong, professor of infectious diseases at UCSF Health, said azelastine may be useful for people already using it for allergies, but argued there is insufficient proof to endorse it broadly.
Chin-Hong said the trial also highlights the potential of nasal mucosa as a target for future vaccines.
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