A polysaccharide compound isolated from red algae with demonstrated antiviral activity against the common cold has shown promise as a preventative agent in COVID-19.
Iota-carrageenan (IC) is a sulphated polysaccharide compound found in species of red algae which has been found to possess anti-viral activity against the common cold in both adults and children. The compound appears to interact with the surface of viral particles, trapping them and hence preventing invasion of cells. Because the primary site of infection with a virus is the nasal mucosa, a team from the Instituto de Ciencia, Argentina, wondered if targeted treatment with IC in the form of a nasal spray, directed towards the nasal mucosa, might block entry of COVID-19 and hence prevent viral replication. The team undertook a pragmatic, randomised, placebo-controlled trial among healthcare workers, including physicians, nurses, caring for those with COVID-19. Participants were randomly assigned on a 1:1 basis to either IC or placebo (the normal saline base) and individuals with either a current COVID-19 symptoms or with antibodies from a prior infection were excluded. Participants assigned to both treatments were asked to self-administered 1 puff to each nostril, four times a day for 21 days and were advised to continue with current COVID-19 requirements, e.g., hand washing, use of PPE etc. The primary outcome of the trial was symptomatic illness confirmed by PCR testing and self-reported COVID-19 symptoms.
A total of 394 healthcare workers were included, with 196 assigned to IC and the remainder to placebo. In the IC group, the mean age of participants was 38.3 years (28.1% female) and the majority (80.1%) had no comorbidities. Overall, 43 participants underwent a PCR test after developing COVID-19 symptoms, of whom only 12 were confirmed as positive. The incidence of COVID-19 in those assigned to IC was significantly different to placebo (2 vs 10), giving an odds ratio (OR) of 0.19 (95% CI 0.05–0.77, p = 0.03). Thus, in those using IC, there was an 80% reduction in the risk of becoming infected.
The authors highlighted how apart from vaccination, their study was the first to demonstrate a prophylactic effect against COVID-19. Moreover, a strength of the study was the fact that it was undertaken in an area with high rates of community transmission of COVID-19, hence participants would also have been exposed to the virus outside of the hospital. In their conclusion, the authors called for further studies in an effort to replicate these findings.
Figueroa JM et al. 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. MedRxiv 2021