To date, there is no effective prophylactic agent to prevent COVID-19. However, the development of symptoms similar to covid19 could be prevented with an aqueous solution of chlorine dioxide (ClO2). This retrospective study evaluated the efficacy of an aqueous solution of ClO2 (CDS) as a prophylactic agent in 1.163 relatives living with COVID19 positive / suspected patients.

Prophylactic treatment consisted of 0,0003% chlorine dioxide solution orally for at least fourteen days. Family members in whom no reports of the development of COVID19-like symptoms were found in the medical history were considered successful cases. The efficacy of CDS in preventing covid19-like symptoms was 90,4% (1.051 of 1.163 family members did not report any symptoms). Comorbidities, sex, and severity of the patient’s illness did not contribute to the development of symptoms similar to covid19 (P = 0,092, P = 0,351, and P = 0,574, respectively). However, older relatives were more likely to develop symptoms similar to those of covid19 (ORa = 4,22, P = 0,002). There was no evidence of alterations in blood parameters or in the QTc interval in relatives who consumed CDS. Recent findings on chlorine dioxide justify the design of clinical trials to evaluate its efficacy in preventing SARS-CoV-2 infection.