Marinomed Biotech AG announced a new study on the antiviral efficacy of iota-carrageenan (Carragelose) against the original SARS-CoV-2 strain and variants of concern (VOC), including the currently predominant Delta variant, has been published in the International Journal of Molecular Sciences. The peer-reviewed study is the result of a collaboration between virologists at the Friedrich-Alexander-Universit-t Erlangen- N-rnberg (FAU) and Marinomed as well as scientists from Ulm University Medical Center and the University Hospital Tuebingen who provided the patient-isolates of SARS-CoV-2 VOCs. In short, the study showed that iota-carrageenan was the most effective of the three carrageenans tested. At a concentration as low as 10 -g/ml, it was able to almost completely block virus replication in Calu-3 human lung cells for all SARS-CoV-2 strains tested, including the highly infectious delta variant. The researchers investigated the antiviral effects of iota-, lambda- and kappa-carrageenan, three sulfated polysaccharides extracted from red seaweed, on the original SARS-CoV-2 strain and the spreading VOCs: Alpha, Beta, Gamma and Delta. SARS-CoV-2 strains isolated from patients were used to infect two different human lung cell models for Coronavirus infection: a transgenic lung cell line made susceptible to SARS-CoV-2 and the Calu-3 human lung cell line, the best studied in vitro model for human lung cell infection. Treatment of these infected cells with iota-carrageenan efficiently blocked the replication of wildtype SARS-CoV-2 and all tested VOCs. The study joins a growing number of publications that support the virus-blocking effects of iota-carrageenan. In addition to inhibiting SARS-CoV-2 replication in vitro, an independent clinical study showed earlier in 2021 that an iota-carrageenan nasal spray can reduce COVID-19 cases in healthcare workers by 80 %. Further, a number of clinical and in vitro studies have demonstrated that iota-carrageenan nasal sprays are also effective against many other respiratory viruses and can block viral replication, reduce symptoms and shorten the duration of infections. Iota-carrageenan appears to be an effective tool against SARS-CoV-2 and its rapidly emerging variants, as well as against other respiratory viruses like rhinovirus A and B, influenza B virus or respiratory syncytial virus (RSV), which is currently spreading among children and causing high numbers of pediatric hospitalizations. Iota-carrageenan nasal sprays are widely available in many countries without a prescription and approved for the use in children as young as one year. The physical mode of action with its broad efficacy against a multitude of respiratory viruses provides additional protection against infections and may also prove useful in future pandemics. This is in line with the latest statement by the German National Academy of Sciences, Leopoldina, calling for broad antiviral therapeutics to fight both the current and future pandemics.