Rapid initiation of nasal saline irrigation: hospitalizations in COVID-19 patients randomized to alkalinization or povidone-iodine compared to a national dataset https://www.medrxiv.org/content/10.1101/2021.08.16.21262044v...
>Conclusion Patients who initiated isotonic saline nasal irrigation after a positive COVID-19 PCR test were 19 times less likely to be hospitalized than the national rate.
Iota-carrageenan nasal sprays can also not only help prevent nasal infection, but can help cure it:
Efficacy of a nasal spray containing Iota-Carrageenan in the prophylaxis of COVID-19 in hospital personnel dedicated to patients care with COVID-19 disease A pragmatic multicenter, randomized, double-blind, placebo-controlled trial (CARR-COV-02) https://www.medrxiv.org/content/10.1101/2021.04.13.21255409v...
> The incidence of COVID19 was significantly lower in the I-C group compared to placebo (1·0% vs 5·0%) (Odds Ratio 0·19 (95% confidence interval 0·05 to 0·77; p= 0·03).
Carrageenan nasal spray may double the rate of recovery from coronavirus and influenza virus infections: Re-analysis of randomized trial data https://pubmed.ncbi.nlm.nih.gov/34128358/
> The increase in recovery rate was 139% for coronavirus infections, 119% for influenza A infections, and 70% for rhinovirus infections.
Here's a list of all the nasal sprays containing one branded iota-carragenan ingredient in every country in which they are licensed: