Women must begin using hormonal contraceptives in advance before they become effective. For some women, hormonal preparations are associated with unpleasant side effects or increased health risks.
A Polio-Free U.S. Thanks to Vaccine Efforts. ... Polio has been eliminated from the United States thanks to widespread polio vaccination in this country. This means that there is no year-round transmission of polio virus in the United States. Since 1979, no cases of polio have originated in the United States.
