Vitamin C reduces COVID-19 risk: real-time meta-analysis of 72 studies (Version 86)

Significantly lower risk is seen for mortality, ICU admission, hospitalization, and recovery. 25 studies from 25 independent teams in 12 countries show significant benefit.

Meta-analysis using the most serious outcome reported shows 21% [14‑27%] lower risk. Results are similar for Randomized Controlled Trials, higher quality studies, and peer-reviewed studies. Clinical outcomes suggest benefit while viral and case outcomes do not, consistent with an intervention that aids the immune system or recovery but may have limited antiviral effects.

Results are robust—in worst case exclusion sensitivity analysis 29 of 72 studies must be excluded before statistical significance is lost.

Control Vitamin C

6 RCTs with 1,420 patients have not reported results (up to 5 years late).

The European Food Safety Authority has found evidence for a causal relationship between the intake of vitamin C and optimal immune system function1,2.

Early cessation of high-dose IV treatment may result in a detrimental rebound effect3. Ongoing treatment is more effective than early cessation: 33% [22‑42%] vs. 16% [-31‑46%].

No treatment is 100% effective. Protocols combine safe and effective options with individual risk/benefit analysis and monitoring. Other treatments are more effective. Dietary sources may be preferred. The quality of non-prescription supplements varies widely and the quantity of the active ingredient may be significantly lower than stated4-6. High doses may increase the risk of kidney stones7, with risk depending on formulation, predisposition, diet, and hydration8. Choi et al. show the highest bioavailability from fruit and vegetable juice. All data and sources to reproduce this analysis are in the appendix.

7 other meta-analyses show significant improvements with vitamin C for mortality10-14, progression15, severity10,14, and cases16.

7 meta-analyses show significant improvements with vitamin C for mortality1-5, progression6, severity1,5, and cases7.