A nasal spray with iota-carrageenan (I-C), a sulfate polysaccharide synthesized from red algae, was found to be associated with a decreased risk for SARS-CoV-2 infection in healthcare workers who were  exposed to patients with the disease, according to results of a randomized, multicenter, double-blind, placebo-controlled trial published in the International Journal of General Medicine.

In this study, investigators randomly assigned healthy adult hospital staff in a 1:1 fashion to receive either I-C 0.17% nasal spray 4 times daily or placebo. The healthcare workers included in the study were exposed to patients with SARS-CoV-2 infection daily. The investigators excluded participants with prior SARS-CoV-2 infection or COVID-19 antibodies. Although the COVID-19 incubation period is up to 14 days, the follow-up period was 21 days since the trial took place in July 2020 — toward the beginning of the COVID-19 pandemic — when less was known about the virus. The primary endpoint was diagnosis of SARS-CoV-2 infection confirmed by reverse transcription polymerase chain reacting testing during the 21-day follow-up period. On each day of the trial, participants completed a survey which asked about COVID-19 symptoms, and they were subsequently tested for SARS-CoV-2 infection if the investigators decided their symptoms were indicative of infection.

Of 394 participants included in the study, the mean age was 38.5 ± 9 years, and 75.1% were women.

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Among the 394 participants, 12 were diagnosed with SARS-CoV-2 infection. The investigators noted that the incidence of SARS-CoV-2 infection was significantly decreased among participants who received I-C nasal spray vs those who received placebo (1% vs 5%). In regard to the risk for incident SARS-CoV-2 infection among participants who received I-C nasal spray, the relative risk reduction was 79.8% (95% CI, 5.3-95.4), and the absolute risk reduction was 4% (95% CI, 0.6-7.4).

Adverse effects were not significantly different between the groups, with 17.3% of participants in the I-C nasal spray group and 15.2% of those in the placebo group reporting mild adverse events (P =.5).

The study was limited by the potential inclusion of participants with SARS-CoV-2 infection at enrollment and the lack of PCR testing among those who remained asymptomatic for the duration of the study.

These “results suggest that the nasal spray with I-C could give significant protection for COVID-19 prophylaxis in healthcare workers managing patients with COVID-19 disease,” the investigators concluded.

Disclosure: Some author(s) declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.


Figueroa JM, Lombardo ME, Dogliotti A, et al. Efficacy of a nasal spray containing Iota-Carrageenan in the postexposure prophylaxis of COVID-19 in hospital personnel dedicated to patients care with COVID-19 disease. Int J Gen Med. 2021;14:6277-6286. doi:10.2147/IJGM.S328486

This article originally appeared on Infectious Disease Advisor