Airborne pathogens, including SARS-CoV-2, are mainly contracted within the airway pathways, especially in the nasal epithelia, where inhaled air is mostly filtered in resting conditions. Mucosal immunity developing after SARS-CoV-2 infection or vaccination in this part of the body represents one of the most efficient deterrents for preventing viral infection. Nonetheless, the complete lack of such protection in SARS-CoV-2 naïve or seronegative subjects, the limited capacity of neutralizing new and highly mutated lineages, along with the progressive waning of mucosal immunity over time, lead the way to considering alternative strategies for constructing new walls that could stop or entrap the virus at the nasal mucosa surface, which is the area primarily colonized by the new SARS-CoV-2 Omicron sublineages. Among various infection preventive strategies, those based on generating physical barriers within the nose, aimed at impeding host cell penetration (i.e., using compounds with mucoadhesive properties, which act by hindering, entrapping or adsorbing the virus), or those preventing the association of SARS-CoV-2 with its cellular receptors (i.e., administering anti-SARS-CoV-2 neutralizing antibodies or agents that inhibit priming or binding of the spike protein) could be considered appealing perspectives. Provided that these agents are proven safe, comfortable, and compatible with daily life, we suggest prioritizing their usage in subjects at enhanced risk of contagion, during high-risk activities, as well as in patients more likely to develop severe forms of SARS-CoV-2 infection.
Keywords: COVID-19; SARS-CoV-2; infection; nasal spray.