Seven hospitals in Turkey applied the treatment protocol with and without vitamin C to study its effectiveness for shortening the duration of illness and prevention of death.

Out of the 237 hospitalized patients, (ages 22-99), one passed away at the age of 70. The patient had severe vitamin D deficiency and underlying heart and lung disease. The remaining 99.58% of patients recovered with broad spectrum, natural immunity. During the study, the researchers found that 97% of all the hospitalized patients were vitamin D deficient. Patients who were severely vitamin D deficient (55%) were more likely to end up in the ICU and be hospitalized longer. A majority (73%) of hospitalized patients also suffered from underlying comorbidities such as diabetes, heart and lung disease.

The researchers found that intravenous vitamin C sped up patient recovery from an average of 45 days in the hospital to 15 days. The study concludes that a "treatment protocol of HCQ, AZM, and zinc with or without vitamin C is safe and effective in the treatment of COVID-19, with high dose IV vitamin C leading to a significantly quicker recovery."