Table 1:

Prophylactic inhibition of COVID-19 infection

Demographic		Treatment		Protection
Baseline subgroup	Onset of case	AZD7442	Placebo	Relative risk reduction
All participants	All cases	23/749	17/372	33% (−26 to 65) reduction
PCR-negative	All cases	6/715	11/358	73% (27 to 90) reduction
PCR-negative	7 days	1/170	6/352	92% (32 to 99) reduction

Participants (adults > 18 years old) with a potential exposure to an affected individual were 1:2 randomized to saline placebo (n = 372) or a single set of intramuscular 300 mg tixagevimab/cilgavimab [(AZD7442) n = 749] in a double-blind, randomized trial (STORMCHASER; NCT04625972). Whilst the primary endpoint, triggered after 35 infection events, of illness occurring up to day 183 post-potential contact, was not met, unplanned post hoc analysis of individuals who were confirmed viral polymerase chain reaction (PCR) test negative at the start of the trial and did not develop disease for 7 days after infusion, to avoid analysis of people infected before infusion, showed marked prophylactic protection [115].