• Statistically significant improvements are seen for mortality, hospitalization, progression, recovery, cases, and viral clearance. 19 studies from 13 independent teams in 4 different countries show statistically significant improvements in isolation (11 for the most serious outcome).• Meta analysis using the most serious outcome reported shows 53% [33‑66%] improvement. Results are similar for Randomized Controlled Trials, similar after exclusions, and similar for peer-reviewed studies. • Results are robust — in exclusion sensitivity analysis 12 of 26 studies must be excluded to avoid finding statistically significant efficacy in pooled analysis.• Efficacy is variant dependent. In Vitro studies suggest a lack of efficacy for omicron [Liu, Sheward, Tatham, VanBlargan]. Monoclonal antibody use with variants can be associated with prolonged viral loads, clinical deterioration, and immune escape [Choudhary]. ADE shown In Vitro [Shimizu]. • No treatment, vaccine, or intervention is 100% effective and available. All practical, effective, and safe means should be used based on risk/benefit analysis. Multiple treatments are typically used in combination, and other treatments may be more effective. Only 27% of casirivimab/imdevimab studies show zero events with treatment. • All data to reproduce this paper and sources are in the appendix.

Percentage improvement with casirivimab/imdevimab (more)

	All studies	Early treatment	Prophylaxis	Studies	Patients	Authors
All studies	53% [33‑66%]****	47% [25‑62%]***	93% [79‑97%]****	26	54,453	386
Randomized Controlled TrialsRCTs	61% [32‑78%]***	63% [42‑76%]****	93% [79‑97%]****	9	21,306	178
Mortality	40% [1‑64%]*	65% [-6‑88%]	-	8	32,929	216
HospitalizationHosp.	42% [17‑59%]**	39% [9‑59%]*	92% [-36‑100%]	12	46,106	133
Cases	80% [39‑93%]**	33% [2‑57%]	85% [74‑91%]****	4	3,265	71