question: There are, except for remdesivir, no approved antivirals for the treatment or prevention of SARS-CoV-2 infections. Iota-carrageenan formulated into a nasal spray has already been proven safe and effective in viral respiratory infections. We explored this antiviral activity in Calu-3, a human respiratory model cell line. A formula of iota-carrageenan and sodium chloride, as a nasal spray, already approved for human use, effectively inhibited SARS-CoV-2 infection in vitro, providing a more substantial reference for further clinical studies or developments.