Povidone iodine (PVP-I) gargles inhibit the SARS-CoV-2 for an hour in patients with COVID-19, according to a recent study from Japan reported earlier this year.¹

Researchers included 35 patients who had Covid-like symptoms in the last 7 days or asymptomatic patients with a cycle threshold (Ct) value less than 40 for SARS-CoV-2 RNA on RT-PCR of saliva. The study did not include patients with thyroid disease or those who had an iodine allergy. The saliva samples were collected by the patients themselves by spitting into a sterile cup at the time of entry into the study. They were then instructed to gargle with PVP-I gargle solution (20 ml diluted 15 times with water) for 20 seconds three times in a day and then rinse their mouths with water. Saliva samples were collected again just after gargling, 30 minutes later, one hour later and after 2 hours. Viral RNA and titers were individually measured at all four time points. The samples were subject to RT PCR to detect and quantify the infectious viral load. Because of insufficient viral titer or undetectable viral RNA, 24 patients were discounted and the final analysis included only 11 patients.

Results published in the Journal of Hospital Infection show a significant decrease in viral RNA copies in the samples taken right after gargling, at 30 minutes and 60 minutes after gargling, compared with before gargling. Similarly, a significant decrease in viral titre (infectious virus particles) was noted immediately after PVP-I gargling and 60 min after gargling, compared with before gargling. Decrease in viral titer after 30 minutes was not of statistical significance, but it was still lower than in the samples collected prior to gargling. These findings have clinical implications. The authors suggest PVP-I gargles as an effective tool to reduce the risk of transmission of infection during orodental examination and/or treatment.¹Â 

PVP-I has been a widely used topical antiseptic for many years. Amongst the other available antiseptics such as chlorhexidine, it has the broadest spectrum of antimicrobial action with activity against Gram‐positive and Gram‐negative bacteria, bacteria spores, fungi, protozoa and several viruses, ² including coronaviruses like SARS-1 and MERS. In vitro studies have also demonstrated the virucidal activity of PVP-I against SARS-CoV-2, the virus causing Covid-19. ^2,3 A single povidone‑iodine gargle can kill 99.99% of corona virus and other viruses within 30 seconds of contact. ^2,4 The multimodal mechanisms of action, rapid onset of action, persistent effect, lack of reported resistance and an excellent safety profile are the other advantages of PVP-I over other commonly available antiseptics. 

Throat is a major reservoir of infection because SARS-CoV-2 is an airborne virus. ⁴ Hence, gargling with an oral antiseptic such as povidone-iodine, may be recommended as a preventive measure for people at risk of infection and to COVID-19 positive patients, complementary to Covid-appropriate behavior such as hand washing, masking (double masking with 3-layered masks), physical distancing, avoiding public places and poorly ventilated closed indoor spaces.

References

1. Seikai T, et al. Gargling with povidone iodine has a short-term inhibitory effect on SARS-CoV-2 in patients with COVID-19. J Hosp Infect. 2022 Jan 15;S0195-6701(22)00006-8. 
2. Bidra AS, et al. 2020. Comparison of in vitro inactivation of SARS CoV-2 with hydrogen peroxide and povidone-iodine oral antiseptic rinses. J Prosthodont [epub ahead of print 30 Jun 2020]. doi:10.1111/jopr.13220.
3. Anderson DE, et al. Povidone-Iodine Demonstrates Rapid In Vitro Virucidal Activity Against SARS-CoV-2, The Virus Causing COVID-19 Disease. Infect Dis Ther. 2020 Sep;9(3):669-675. 
4. Garg P. Role of povidone‑iodine gargles in Covid‑19 pandemic and a ray of hope for future. J Family Med Prim Care. 2021;10:3941-2.