The HPV Vaccine Protects Against Human Papillomavirus (HPV) That Causes

The HPV vaccine protects against human papillomavirus (HPV) that causes cancer. It protects both the person getting the vaccine and the sexual partners of that person. When calculating the marginal social benefit of the vaccine, it is necessary to include

A) only the marginal private benefit.
B) only the marginal external benefit.
C) both the marginal private benefit and the marginal external benefit.
D) either the marginal private benefit or the marginal external benefit, whichever is larger.