One dose is about 93% effective while two doses of the vaccine are about 97% effective at preventing measles. In the United States, reported cases of measles fell from 3 to 4 million with 400 to 500 deaths to tens of thousands of cases per year following introduction of two measles vaccines in 1963 (both an inactivated and a live
attenuated vaccine (Edmonston B strain) were licensed for use, see chart at right). Increasing uptake of the vaccine following outbreaks in 1971 and 1977 brought this down to thousands of cases per year in the 1980s. An outbreak of almost 30,000 cases in 1990 led to a renewed push for vaccination and the addition of a second vaccine to the recommended schedule. No more than 220 cases were reported in any year from 1997 to 2013, and the disease was believed no longer
endemic in the United States. In 2014, 667 cases were reported. The benefits of measles vaccination in preventing illness, disability, and death have been well documented. Within the first 20 years of being licensed in the U.S., measles vaccination prevented an estimated 52 million cases of the disease, 17,400 cases of
intellectual disability, and 5,200 deaths. From 1999 to 2004 a strategy led by the WHO and
UNICEF led to improvements in measles vaccination coverage that averted an estimated 1.4 million measles deaths worldwide. The vaccine for measles led to the near-complete elimination of the disease in the United States and other developed countries. Measles vaccination averted 57 million deaths between 2000 and 2022, as per
World Health Organization report. Measles is
common worldwide. Although it was declared eliminated from the U.S. in 2000, high rates of vaccination and excellent communication with those who refuse vaccination are needed to prevent outbreaks and sustain the elimination of measles. This individual returned to a community with many unvaccinated children. The resulting outbreak infected 34 people, mostly children and virtually all unvaccinated; three of them were hospitalized. The public health response required making almost 5,000 phone calls as part of
contact tracing, arranging and performing testing as needed, and arranging emergency vaccination for at-risk people who had had contact with this person. When addressing the major U.S. measles outbreak in 2019, the
Centers for Disease Control and Prevention stated that outbreaks are more likely in areas with pockets of unvaccinated residents. However, during the U.S. outbreak beginning in February 2025, the agency declined to publicize their updated expert assessment and forecasting model supporting this conclusion, thereby choosing not to alert clinicians and the public of being at specific risk in areas with low immunization rates. The vaccine has
nonspecific effects such as preventing respiratory infections, that may be greater than those of measles prevention alone.