"There are tens of millions that would go for this vaccine, how can he NOT have companies beating down his door?

Every afflicted single person would be buying this vaccine for their SO in a heartbeat."

yes, but there is a limitless supply of money for companies that are selling treatments to the infection, as people must keep buying these over and over. Once a vaccine is made, the pot of money dries up. Unfortunate, but vaccines are not good investments for businesses.