It is certainly good to study multiple coronavirus vaccines at this point, but that is not what I mean by this question. What I mean is: suppose a vaccine appears safe and effective from trials, is approved, and we are starting to vaccinate at scale. Should we continue developing other vaccines? Presumably we should if there are serious side effects of the first vaccine, it isn't as effective as we like, etc. But what if we don't expect any other vaccine that is being studied to do any better in trials? I can still see arguments to develop additional vaccines, and once we have multiple approved vaccines, if they perform roughly equivalently, to randomize which vaccine we give to people. Reasons include:
We might find out that there are long-term adverse consequences of one of the vaccines (and we might find this out only much later). Using multiple vaccines will allow us to easily switch in this case. Also, we won't have exposed pretty much the entire human population to the risk.
It would reduce the financial risk of vaccine development now to know there will be multiple "winners", perhaps encouraging additional vaccine development, and perhaps reducing the incentive to cut corners to be first.
Is there any theory for how to think about these questions? Are people thinking about them? What are some references?