It would be administered to stop ongoing infections. The article does not say how long the antibodies persist at effective levels.
IOW, an effective treatment, not a vaccine. OTOH wouldn’t being exposed to Covid itself stimulate the immune system to create immunity?If you know your treatment is 100% (well, 99.9%) effective, couldn’t you deliberately infect someone you want to protect and, after a calibrated interval, kill off the infection with your synthetic antibodies - and get a health care worker (or other “essential” worker) who was immune?
Sorta like an "attenuated live virus” vaccination - except the attenuation occurs after its introduction into the patient.