Nasal sprays available over-the-counter, historically noted for their safety and efficacy in treating seasonal allergies, could be perceived in a new light following clinical trial results released on Tuesday.

The antihistamine azelastine has been observed to have antiviral properties against various respiratory infections, including Influenza, RSV, and viruses responsible for COVID, according to a growing body of research.

Researchers from Saarland University Hospital in Germany conducted a study involving 450 adults, predominantly in their early 30s. One group of 227 participants used a nasal spray three times daily, while the other 223 received a placebo spray under the same regimen.

Throughout nearly two months, all participants underwent COVID rapid testing twice weekly. The results indicated that the incidence of symptomatic infections was 2.2% in the azelastine group, markedly lower than the 6.7% infection rate in the placebo group.

Furthermore, azelastine seemed to diminish the incidence of other symptomatic respiratory infections, as highlighted in a study published in JAMA Internal Medicine.

While researchers remain uncertain about the exact mechanism by which azelastine limits infections, they hypothesize that it may bind to the virus in the nasal mucosa.

Another possibility is that azelastine interacts with the ACE2 receptor, the primary entry point for COVID viruses into human cells, thereby preventing their attachment.

“Our findings imply that azelastine could serve as a scalable and commercially viable preventive measure against COVID, especially in high-risk scenarios such as crowded indoor events and travel,” the researchers noted.

However, the study had limitations, including that all participants were relatively young and healthy, according to the researchers.

Valz emphasized that azelastine should not replace vaccination and further research is essential before considering it as a standard precautionary measure for the public, particularly for vulnerable groups.

Dr. William Messer, associate professor at Oregon Health & Science University, found the results “rationally convincing” in terms of risk reduction, but pointed out the intensive regimen of daily sprays in the trial.

He questioned whether wearing a mask might be a simpler approach to preventing COVID infection.

“Masks can be inconvenient and bothersome, yet may be easier to adhere to than remembering to use three nasal sprays daily,” Messer remarked.

Nevertheless, he added, “I do not discourage anyone who wishes to try it.”

Other researchers are seeking more data to ascertain the effectiveness of nasal sprays in high-risk populations, such as the elderly and immunocompromised individuals who require additional preventive measures.

Dr. Peter Chin-Hong, a professor at UCSF Health specializing in Infectious Diseases, speculated that azelastine could serve as an additional COVID-blocking tool for individuals already using nasal sprays for seasonal allergies, although he believes the evidence is insufficient for broader recommendations.

“While the potential is promising, I believe now is not the appropriate time to recommend it as a COVID preventative,” he stated in an email. “For those over 65, I continue to advocate for vaccination as the primary defense against COVID.”

Nonetheless, Chin-Hong highlighted that the trial results underscore the importance of targeting the nasal mucosa in developing future vaccines against COVID and other respiratory viruses as a more effective means of infection prevention.

“Current COVID vaccines have not proven to be highly effective in preventing infection,” he remarked. “There is a need for more mucosal vaccines for respiratory viruses. While flu vaccines are widely used, ongoing efforts are being made to create mucosal vaccines for coronaviruses, necessitating continued advocacy for federal support and prioritization for these initiatives.”