Epidemiologic Notes and Reports Mumps -- United States, 1985-1986

In 1985, 2,982 cases of mumps were reported in the United States, representing an annual incidence rate of 1.2 cases/100,000 population (Table 6). This was 1.3% lower than the 1984 total of 3,021 cases and was an all-time low in reported mumps cases. It represented a 98% decrease from the peak of 152,209 cases reported in 1968, the year mumps became a nationally notifiable disease and the first year after mumps vaccine licensure, in December 1967.

In 1986, a provisional total of 6,807 mumps cases (2.8 cases/100,000 population) was reported. This is more than double the number of cases reported in 1985. It marked the first increase in reported mumps since 1982 and was the highest number of reported cases since 1980 (Figure 1). Nevertheless, it represented a 95.6% decrease from 1968.

Provisionally, 23 of the 47 states where mumps is a notifiable disease* reported more mumps cases in 1986 than in 1985. Maine and Wyoming reported no mumps cases. By comparison, in 1985, 16 states reported more mumps cases than in 1984, and two states (Louisiana and South Dakota) reported no mumps cases. Mumps cases were reported from 22.8% of 2,982 reporting counties in 1985, as compared with 23.3% of reporting counties in 1984. Age and county data are not yet available for 1986.

Illinois (2,743 cases, 23.7/100,000) and Tennessee (1,174 cases, 24.4/100,000) accounted for more than one-half of all mumps cases provisionally reported in 1986. Illinois and Tennessee are two of 16 reporting states without laws requiring mumps immunization for school entry or attendance. Although these 16 states comprise less than one-fourth of the U.S. population, they accounted for more than two-thirds of reported mumps cases.

National age-specific data are available for 2,579 (86.5%) of the persons with mumps cases reported for 1985 (Table 6). As in the prevaccine era, persons under 15 years of age continued to have the highest reported incidence rate (4.1 cases/100,000 population) (1). In contrast, the rate for persons 15 years of age or older was 0.4/100,000. Mumps patients 5-19 years of age accounted for 73.3% of persons of known age reported in 1985.

Long-term age-specific data on mumps patients are available from three reporting areas (California, Massachusetts, and New York City) that have been continually collecting such data since the time of vaccine licensure (Table 7). In the decade immediately following vaccine licensure (1967-1976), 5- to 9-year-olds had the highest reported incidence rate; children under 5 had the second highest rate. Together, these two groups accounted for over 70% of all reported cases. Over the last 5 years (1981-1985), these two age groups accounted for slightly more than 50% of reported cases. Although the proportion of cases occurring in older persons has been increasing, their risk of disease has markedly decreased. Compared with the risk of acquiring mumps at the beginning of the vaccine era (1967-1971), the risk during the period 1981-1985 decreased at least 90% for all age groups. Reported by State and Territorial Epidemiologists; Surveillance, Investigations, and Research Br, Div of Immunization, Center for Prevention Svcs, CDC.

Editorial Note

Editorial Note: The incidence of mumps reported in the United States increased in 1986 after 15 years of almost continual decline (Figure 1). Although age-specific data for 1986 are not yet available, reports from Illinois, Tennessee, and several other states suggest that the increased mumps activity was largely a result of illness in unvaccinated middle and high school students. The age-specific changes in mumps epidemiology observed since vaccine licensure are similar to those noted for measles and rubella and reflect a vaccination policy oriented toward preschool and elementary schoolchildren (2).

Persons who were neither vaccinated nor infected at a young age may be exposed when they are older and at higher risk for mumps-associated complications. This group now accounts for the majority of reported cases. The pool of susceptible persons remaining among older school-aged children and young adults has the potential for allowing continued transmission in middle and high schools and, eventually, in colleges and places of employment. Available data suggest that mumps outbreaks among unvaccinated cohorts will continue. This was evidenced by the outbreaks among middle and high school students in Ohio in 1982 (3,4) and New Jersey in 1983 (5). In September 1984, Ohio passed a law requiring mumps immunization for children in kindergarten through grade 12 (K-12), and, with gradual enforcement of the law, has reduced reported mumps substantially (6). In response to the 1986 outbreak, Illinois has recently enacted a K-12 law and will require all students to be in compliance as of fall 1987.

The effectiveness of mumps school immunization laws in decreasing mumps incidence has been consistently demonstrated (1,4-8). Sixteen of the 47 states reporting mumps currently do not require proof of mumps immunity for school entry (Table 8). Of the 31 states that do require mumps immunization, 11 have laws that affect only initial entry into school; six have laws that affect children beyond first grade but do not comprehensively include grades K-12; and 14 require proof of mumps immunity for all students in grades K-12. In 1985, the incidence rate of mumps in states with no law was twice that of states with a comprehensive K-12 school law. In 1986, the rate was 12-fold higher in states without a law and 2.6-fold higher if Illinois and Tennessee are excluded from the analysis because of their unusually high incidence of mumps. Of note, the reported mumps incidence rate during 1985 and 1986 in states with only a "partial law" (i.e., a school entry law or other law not comprehensively including grades K-12) was no different than that in states with no school law (again excluding Illinois and Tennessee for 1986).

Before the routine use of measles-mumps-rubella (MMR) vaccine in recent years, mumps immunization levels were considerably lower than measles or rubella immunization levels. This was partly because of the relatively high cost of mumps vaccine compared with the cost of either measles or rubella vaccines. In addition, mumps has never been given the same priority as measles or rubella in the public or medical community, despite the morbidity due to mumps and the fact that mumps virus was a leading cause of acquired deafness in the prevaccine era and the leading cause of viral encephalitis of known etiology in the United States until 1975 (1). Mumps vaccine was not recommended for routine use in all susceptible children until December 1977 (9). Nevertheless, mumps vaccine has been consistently shown to be highly cost-beneficial (10,11) and to be safe and effective, with reported clinical efficacy in the range of 75%-90% (2,12,13).

Children and adults lacking adequate documentation of physician-diagnosed mumps or vaccination with live mumps vaccine on or after their first birthday should receive mumps vaccine. It is especially important that susceptible adults be vaccinated because of the increased risk of mumps-associated complications (1). MMR is the vaccine of choice in recipients likely to be susceptible to measles and/or rubella as well as to mumps. There is no increased risk associated with vaccinating persons who may already be immune.

Future policy emphasis should include enforcing existing laws requiring vaccination against mumps, extending present laws to comprehensive K-12 coverage, and considering the introduction of laws requiring vaccination for all students in grades K-12 in states without an existing law. The recommendation of the American College Health Association that all college health programs require documentation of previous mumps disease or vaccination for entering students should be followed (14).

References

1. CDC. Mumps surveillance report, January l977-December 1982. Atlanta, Georgia: US Department of Health and Human Services, Public Health Service, 1984.

2. ACIP. Mumps vaccine. MMWR 1982;31:617-20,625.

3. CDC. Efficacy of mumps vaccine--Ohio. MMWR 1983;32:391-2,397-8.

4. CDC. Mumps--United States, 1980-1983. MMWR 1983;32:545-7.

5. CDC. Mumps outbreak--New Jersey. MMWR 1984;33:421-2,427-30.

6. Ohio Department of Health. Mumps immunization and disease. Preventive Med Monthly 1986;9(7):1-2.

7. CDC. Mumps--United States, 1983-1984. MMWR 1984;33:533-5.

8. CDC. Mumps--United States, 1984-1985. MMWR 1986;35:216-9.

9. ACIP. Mumps vaccine. MMWR 1977;26:393-4.

10. Koplan JP, Preblud SR. A benefit-cost analysis of mumps vaccine. Am J Dis Child 1982;136:362-4.

11. White CC, Koplan JP, Orenstein WA. Benefits, risks and costs of immunization for measles, mumps and rubella. Am J Public Health 1985;75:739-44.

12. Kim-Farley R, Bart S, Stetler H, et al. Clinical mumps vaccine efficacy. Am J Epidemiol 1985;121:593-7.

13. Sullivan KM, Halpin TJ, Marks JS, Kim-Farley R. Effectiveness of mumps vaccine in a school outbreak. Am J Dis Child 1985;139:909-12.

14. American College Health Association. Position statement on immunization policy. J Am College Health 1983;32(1):7-8. *Mumps is not notifiable in New Mexico, Oklahoma, and Oregon.

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