Maurice Ralph Hilleman developed vaccines at the Merck Institute of Therapeutic Research in West Point, Pennsylvania, during the twentieth century. Over the course of his career at Merck, Hilleman created over forty vaccines, making him one of the most prolific developers of vaccine in the twentieth century. Of the fourteen vaccines commonly given to children in the US by 2015, Hilleman was responsible for eight of them. Hilleman's most widely used vaccine was his measles, mumps, and rubella (MMR) vaccine. Hilleman's MMR vaccine prevented many diseases and also rubella in millions of children and pregnant women. Rubella in pregnant women often led to congenital rubella syndrome in the fetus, causing severe malformations.

In 2006, the United States branch of Merck & Co. received FDA approval for Gardasil, a human papillomavirus, or HPV, vaccine that protects against HPV and the cervical cancer that can come with it. In 1891, George F. Merck founded the US branch of the company to distribute chemicals with high purity for use in research, in New York City, New York, and other areas nearby. HPV is a common sexually transmitted infection that can cause genital warts, regular skin warts, cervical cancer, and other cancers. Since 2016, Gardasil has been the only HPV vaccine in use in the US and over people received 28 million doses in the country between 2014 and 2017, reducing people’s chances of contracting cancer.

The measles, mumps, and rubella (MMR) vaccine was created by Maurice Hilleman in 1971 at the Merck Institute of Therapeutic Research, a pharmaceutical company in West Point, Pennsylvania. It combined three separate vaccines for measles, mumps, and rubella, common and sometimes fatal diseases. Measles causes a red skin rash and severe fevers that can be fatal. Mumps causes fever and swelling of the salivary glands in the mouth and jaw, while rubella causes milder fevers and skin rashes. Pregnant women that contract rubella sometimes pass the virus to their fetuses, causing congenital rubella syndrome, which results in malformations of the eyes, ears, heart, and brain in the fetuses. The MMR vaccine has protected millions of people from contracting the potentially deadly diseases of measles, mumps, and rubella, as well as prevented the development congenital rubella syndrome in the fetuses.