It was not blinded. It was open-label and the outcomes were subjective (ICU admission). The doctors involved with the trial knew who got what and may have biased their actions based on that. Given the subjective outcome and small number of participants, this is particularly important. The trial would be slightly underpowered even if it were blinded.
Other studies on Vitamin D are retrospective cohort / observational studies which are heavily biased with possible confounders with respect to Vitamin D.
My personal opinion is that Vitamin D may help in COVID-19 but this trial does not 'confirm' that. Someone should run a similar trial with more participants and/or a fully blinded trial / a trial with more outcomes (biomarkers, etc).
Other studies on Vitamin D are retrospective cohort / observational studies which are heavily biased with possible confounders with respect to Vitamin D.
My personal opinion is that Vitamin D may help in COVID-19 but this trial does not 'confirm' that. Someone should run a similar trial with more participants and/or a fully blinded trial / a trial with more outcomes (biomarkers, etc).