The principal route of spread of severe acute respiratory syndrome coronavirus 2 (SARSCoV-2) is via respiratory droplets produced from the contaminated nasopharyngeal secretions. A randomized clinical trial was conducted in persons older than 18 years to examine if povidone-iodine (PVP-I) applied to the nasopharynx reduced the viral load in patients who had symptoms of coronavirus disease (COVID-19). All the study participants had their nasopharyngeal samples evaluated in the last 48 hours and tested positive for SARSCoV-2 ribonucleic acid (RNA) by reverse transcription polymerase chain reaction (RT-PCR) test with Ct (cycle threshold) value of ≤20. Patients with a history of thyroid disease were not included in the study group.

The viral load was quantified again at the start of the study following which the patients were randomised into two groups of 12 each:  a control group with no intervention and an intervention group involving 4 consecutive mouthwashes and gargles with 25 mL of 1% aqueous PVP-I and intranasal application of 10% PVP-I ointment. Safety and efficacy was evaluated on Day 1 of the trial and then every 2 days until the seventh day. A negative viral titer was noted in 11 patients. The viral load was found to reduce and in the intervention group, the mean relative difference in viral titers between baseline and day 1 was 75% (95% CI, 43%-95%), while in the control group, this difference was found to be 32% (95% CI, 10%-65%), although these differences were not statistically significant. 

This study had a small number of subjects. The authors recommend a larger trial to further validate the benefit of PVP-I in reducing the viral load in the respiratory secretions and thus the person to person spread of the virus, using PVP-I in lower concentrations to minimize adverse effects.