“Scientists were close to a coronavirus vaccine years ago. Then the money dried up.”
the money dried up for two reasons
a) yes, they want to see if it’s something that will come back unchanged year after year,
but the biggest reason is:
b) lack of humans willing to become deliberately infected, at a time when SARS had disappeared and wasn’t circulating and with no cure should the volunteers take a turn for the worse. Such act being unethical and likely illegal even with consent.