If a positive externality in consumption exists, how might the market equilibrium price and quantity differ from the socially optimal outcome?

When a positive externality in consumption exists, it means that when people consume a good, they also create benefits for others who are not directly involved in the transaction. For example, if many people get vaccinated, not only do they protect themselves from illness, but they also reduce the risk of spreading disease to others. In a free market, the price and quantity of the vaccine may be lower than what is socially optimal because the benefits to society are not fully reflected in the market price. This can lead to fewer vaccinations than is ideal, meaning that the market equilibrium does not account for the extra benefits created for society. Therefore, the socially optimal outcome would involve a higher quantity of the good being consumed at a higher price that reflects the total benefits to everyone.