• 96% of 23 vitamin D treatment studies report positive effects (13 statistically significant in isolation).• Random effects meta-analysis with pooled effects using the most serious outcome reported shows 78% and 53% improvement for early treatment and for all studies (RR 0.22 [0.12-0.43] and 0.47 [0.36-0.60]). Results are similar after restriction to 17 peer-reviewed studies: 81% and 55% (RR 0.19 [0.06-0.61] and 0.45 [0.33-0.61]).• Heterogeneity arises from many factors including treatment delay, patient population, the effect measured, variants, the form of vitamin D used, and treatment regimens. The consistency of positive results across a wide variety of cases is remarkable. The only treatment study reporting a negative effect is a very late stage cholecalciferol study.• Sufficiency studies show a strong association between vitamin D sufficiency and outcomes. Meta analysis of the 52 studies with pooled effects using the most serious outcome reported shows 53% improvement (RR 0.47 [0.40-0.55]).• While many treatments have some level of efficacy, they do not replace vaccines and other measures to avoid infection. Only 4% of vitamin D treatment studies show zero events in the treatment arm. Multiple approaches are required to protect everyone from all existing and future variants.• All data to reproduce this paper and the sources are in the appendix.

	Improvement	Studies	Authors	Patients
Treatment RCTs	50% [14‑71%]	5	56	1,370
Treatment studies	53% [40‑64%]	23	236	23,046
Calcifediol/calcitriol treatment	62% [43‑75%]	4	43	7,095
Treatment mortality	63% [45‑75%]	14	127	8,818
Sufficiency studies	53% [45‑60%]	52	419	12,067