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Vaccines cause herd immunity. If the majority of people in a community have been vaccinated against a disease, an unvaccinated person is less likely to get the disease since others are less likely to become sick from it and spread the disease.
There are approximately 3 million unintended pregnancies in the United States each year.
The first-known contraceptive was crocodile dung, used in Egypt in 2000 BC. Condoms were also reportedly used, made of animal bladders or intestines.
Nitroglycerin is used to alleviate various heart-related conditions, and it is also the chief component of dynamite (but mixed in a solid clay base to stabilize it).
HIV testing reach is still limited. An estimated 40% of people with HIV (more than 14 million) remain undiagnosed and do not know their infection status.