Prophylactic Treatment With Carragelose Nasal Spary to Prevent SARS-CoV-2, COVID-19, Infections in Health Care Workers

This is a prospective, randomized placebo-controlled double blinded clinical trial in frontline healthcare workers managing COVID-19 patients. Screening - first day of treatment: After signing the informed consent form eligible participants will be included. Immediately after inclusion and after first nasal swab, participants start with their first treatment. In order to obtain nasal swabs and to assess adverse events the participants will visit the sites on a weekly basis over a period of 12 weeks. 3 times a day for 84 days (12 weeks): * 1 puff of Coldamaris pro. nasal spray into each nostril (1.2 mg/ml; 140 µl per puff) and * 3 puffs of Coldamaris pro. nasal spray into mouth Weekly sampling for testing of SARS-CoV-2 and respiratory virus panel (Influenza A, Human Metapneumovirus, Influenza A - subtype H1 Adenovirus, Influenza A - subtype H3 Parainfluenza 1, Influenza A - subtype 2009 H1N1, Parainfluenza 2, Influenza B Parainfluenza 3, SARS-CoV-2 Parainfluenza 4, Coronavirus HKU1 Respiratory Syncytial Virus A, Coronavirus N63L, Respiratory Syncytial Virus B, Coronavirus OC43, Rhinovirus/Enterovirus, Coronavirus 229E, Human Bocavirus) At begin and end of trial blood samples will be taken for differential blood count and for serology. The primary end point of the is the presence of COVID-19 symptoms including symptoms of respiratory viral infection. The primary hypothesis is a reduction of symptom days caused by SARS-CoV-2 and/or respiratory viral infection in health care workers treated with Coldamaris pro. nasal spray compared to placebo treated ones