A study published in the American Journal of Medicine evaluated the efficacy of a nitric oxide generating lozenge

A study published in the American Journal of Medicine evaluated the efficacy of a nitric oxide generating lozenge (throat drop) in outpatients with newly diagnosed COVID-19 to mitigate severity. The study was done in 2020 on 524 patients in the United States ages 50-85 who were African American or Latino with a recent COVID -19 diagnosis and at least one of the following risk factors: chronic kidney disease, chronic obstructive pulmonary disease, heart disease, diabetes, obesity and smoking. Patients were randomly enrolled into one of two groups: a group that took two nitric oxide generating lozenges a day for 30 days and a group that took two placebo lozenges a day for 30 days. Clinicians who did know who was in which of the two groups called the patients at least twice a week to gather a variety of data, including whether the patient had been hospitalized. Patients were also asked to contact the study center or ask a family member to contact the study center for any change in their conditions. The group getting the nitric oxide lozenges did not show a significant reduction in the risk of being hospitalized due to COVID-19 as compared with the placebo group. Did the researchers use any blinding? If so, what was blinded? Explain your answers