Honest question, not intended to be a leading question....

Influenza is caused by a virus. We have grown the virus for many years and killed it to be included in flu vaccines. Why can we not do the same for the China variant of the corona virus? Is there a structural or chemical or other reason why we are unable to replicate our previous "successes" and must look for a new approach? Not looking here for the routine answers - big pharma profits, Bill Gates conspiracy, NWO control, etc. Looking for a legitimate bio/med explanation.