The problem is that this is a money-losing proposition. If ten companies attempt to produce a vaccine, spending X, and two of them succeed (before the rest), wi

The problem is that this is a money-losing proposition. If ten companies attempt to produce a vaccine, spending X, and two of them succeed (before the rest), with the government paying each double their development costs (2X), that means that the expected outcome of developing a vaccine is -0.6X. As a result, we should expect that most companies will only make a token effort.