Before the introduction of measles, mumps and rubella vaccine in America during 1963 nearly every child in the country had contracted one of the diseases at some point in their childhood. Before this, as per data released by CDC around half a million new cases were recorded between 1942 and 1962. During this period around 4 million people used to be infected each year but several cases went unreported and of these around 400–500 died every year while 48,000 received treatment and around a thousand people contracted encephalitis.
But the situation improved drastically after introduction of MMR vaccine that led to strong plummet in measles cases. When there was a resurgence of measles cases during 1980 and 1990 health officials asked parents to given their children two doses of MMR instead of one. This was to ensure that parents that did not get their vaccinated due to lack of insurance would get it through the Vaccines for Children Program which was introduced in 1993 to provide vaccine to children that did not have insurance. These sustained efforts helped in eradicating the disease to a large extent and finally in 2000 the CDC declared that USA was finally free of measles.
Though people no longer considered measles as a threat, a study published by Dr. Andrew Wakefield in 1998 in which he claimed that MMR vaccine caused autism led to anti-vax movement that caused parents to stop getting their children vaccinated. Though seven different nations carried out eighteen studies across three continents to prove that MMR vaccine did not cause autism it still did not allay the fear of the vaccine from several concerned parents. This has led to resurgence in measles since 2016 within US and around the world where parents have not vaccinated their children there is 300 % increase in new measles cases. In US this year alone there have been 940 new cases of measles among unvaccinated children.