Measles Elimination in the United States

Abstract

In 1962, immediately preceding the licensure of the first measles vaccines in the United States, when measles was a nearly universal disease, Alexander Langmuir described the medical importance of measles to the country and put forth the challenge of measles eradication [1]. Although most patients recovered without permanent sequelae, the high number of cases each year made measles a significant cause of serious morbidity and mortality Langmuir showed that >90% of Americans were infected with the measles virus by age 15 years [1]. This equated to roughly 1 birth cohort (4 million people) infected with measles each year. Not all cases were reported to the public health system; from 1956 to 1960, an average of 542,000 cases were reported annually.By the late 1950s, even before the introduction of measles vaccine, measles-related deaths and case fatality rates in the United States had decreased markedly, presumably as a result of improvement in health care and nutrition. From 1956 to 1960, an average of 450 measles-related deaths were reported each year (∼1 death/ 1000 reported cases), compared with an average of 5300 measles-related deaths during 1912–1916 (26 deaths/ 1000 reported cases) [2]. Nevertheless, in the late 1950s, serious complications due to measles remained frequent and costly. As a result of measles virus infections, an average of 150,000 patients had respiratory complications and 4000 patients had encephalitis each year; the latter was associated with a high risk of neurological sequelae and death. These complications and others resulted in an estimated 48,000 persons with measles being hospitalized every year [3]. In 1966, 3 years after licensure of the first measles vaccines, Sencer et al. [4] announced the first of 3 efforts to terminate indigenous measles transmission in the United States. Subsequent measles-elimination goals were announced in 1978 and in 1993. The fundamental strategy for all 3 elimination efforts consisted of achieving high vaccination coverage among preschool- and school-aged children, careful surveillance of cases, and rigorous outbreak control [4–6]. Although the first 2 elimination efforts did not achieve elimination, they resulted in a substantial reduction in measles incidence: An average of 1.3 cases per 100,000 population was reported during 1982–1988, compared with an average of 313 cases per 100,000 during 1956–1960 (figure 1). Nevertheless, a resurgence of measles occurred during 1989–1991, again demonstrating the serious medical burden of the disease. More than 55,000 cases, 123 deaths, and 11,000 hospitalizations were reported [7]. Two major causes of this epidemic were vaccine failure among a small percentage of school-aged children who had received 1 dose of measles vaccine and low measles vaccine coverage among preschool-aged children.