For other coronaviruses that infect humans there the adaptive immune response isn't particularly strong and doesn't last. E.g. immunity to HCoV-OC43 lasts no m

For other coronaviruses that infect humans there the adaptive immune response isn't particularly strong and doesn't last. E.g. immunity to HCoV-OC43 lasts no more than about 12 months. This is a reason to suspect that a vaccine may not be easily developed; so antibody therapy (and/or anti-virals) might be the best we can do. If the antibody therapy was highly effective and could be produced at scale for a tolerable cost, it would probably be a pretty effective tool. Though monoclonal antibodies aren't known for being particularly affordable.