Statistically significant improvements are seen in treatment studies for mortality, ICU admission, hospitalization, and cases. 36 studies from 33 independent teams in 16 different countries show statistically significant improvements in isolation (25 for the most serious outcome).

•Random effects meta-analysis with pooled effects using the most serious outcome reported shows 74% [45‑88%] and 38% [31‑44%] improvement for early treatment and for all studies. Results are similar after restriction to 69 peer-reviewed studies: 70% [37‑85%] and 38% [31‑45%], and for the 44 mortality results: 76% [37‑91%] and 37% [25‑47%].

•Acute treatment (early 74% [45‑88%], late 48% [32‑61%]) shows greater efficacy than chronic prophylaxis (31% [22‑39%]), suggesting that long-term supplementation may not be ideal.
•Late stage treatment with calcifediol/calcitriol shows greater improvement compared to cholecalciferol: 73% [57‑83%] vs. 38% [20‑52%].

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