Perhaps the inactivated coronavirus vaccines such as the Indian Covaxin might be something to consider. Covaxin is a based upon an unmodifed early strain that is chemically inactivated and boosted with an adjuvent; it possess all the wild-type anitgens, include the N-protein, and should theoretically produce an immune response similar to natural infection. Apparently the adjuvent used helps induce a strong Th1 adaptive immune response.