Practise identifying positive or negative third-party effects, separating them from private costs and benefits and linking externalities to market failure and intervention.
A medical team provides vaccinations for children to prevent an outbreak of an infectious disease.
Why would this be described as a positive externality?
Additional benefit might be gained as the disease no longer spreads.
Any kind of medical help will improve the condition of the children.
No action would be taken unless the medical team intervened.
The social benefits of vaccination are less than the social costs.
A