Is a vaccine a public good?

Prabhudesai asked: Is a vaccine a “public good”?

In economics, goods that are non-rival (consumption of the good by someone does not decrease the amount available for others to consume) and non-excludable (no one can be prevented from consuming) are called pure public goods. By that definition, clearly a vaccine is not a pure public good.

A good that is non-rival but excludable is called a “club good” — a large park in a gated community, for example. A good that is rival but non-excludable is called “common pool” — a pasture for grazing cattle with no fences, for example. 

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