Current Trends Measles -- Los Angeles County, California, 1988

A provisional total of 513 confirmed cases of measles was reported from Los Angeles County during 1988 (Figure 1). The Los Angeles County cases represent 17.5% of all (2933) cases reported for the United States during this period and an incidence rate of 6.4 cases/100,000 persons--a risk 5.3 times higher than that in the rest of the United States (1.2/100,000). In early 1988, school-aged children and adults were predominantly affected. However, in May, both the number and proportion of cases reported among children less than 5 years of age increased, prompting a more intense investigation. The following analysis is based on the provisional total of 355 persons with confirmed cases having onset from May 1 to December 31.

Of 353 confirmed patients with known ages and onset from May 1 to December 31, 228 (64.6%) were less than 5 years of age (Table 1). A total of 135 (38.2%) were less than 16 months of age (i.e., too young for routine vaccination), including 87 (24.6%) less than 12 months of age; 93 (26.3%) were 16 months to 4 years of age. Infants less than 12 months of age had the highest reported age-specific incidence rate (66.9/100,000) (Table 1). Race/ethnicity was known for 331 (93.2%) patients; of these, 257 (77.6%) were Hispanic. The risk for measles for Hispanics (11.3/100,000) was 3.6 times that for black non-Hispanics (28 cases; 3.1/100,000) and 12.6 times that for white non-Hispanics (31 cases; 0.9/100,000).

Preventability status* was known for 353 (99.4%) of the cases; 150 (42.5%) of these were preventable, and 203 (57.5%) were considered programmatically nonpreventable. However, among the 90 vaccine-eligible preschoolers aged 16 months to 4 years for whom preventability status was known, 77 (85.6%) had preventable measles. Of the 203 patients with nonpreventable illnesses, 135 (66.5%) were in children younger than the recommended age for routine vaccination, and 50 (24.6%) were in previously vaccinated persons. Of the remaining 18 (8.9%) patients with nonpreventable measles, five had a philosophic exemption or a medical contraindication to receiving the vaccine, and 13 were born before 1957.

The setting of transmission was known for 209 (58.9%) patients, of whom 120 (57.4%) had known household exposures to measles. Sixty-three (30.1%) acquired measles in medical settings, where transmission occurred both among and between patients and personnel. Transmission also occurred in day-care centers, schools, and colleges.

One hundred twenty-two (34.4%) patients were hospitalized. The reported age- specific hospitalization-to-case rate was similar for infants (43.7%) and preschool- aged children (1-4 years of age) (38.3%), slightly lower for adults greater than or equal to20 years of age (32.7%), and lowest for persons 5-19 years of age (17.1%). Of the 355 patients, 60 (16.9%) had diarrhea, 37 (10.4%) had otitis media, 35 (9.9%) had pneumonia, three (0.8%) had encephalitis, and two (0.6%) had meningitis. One adult patient with hemophilia and human immunodeficiency virus-related illness was probably exposed to measles at the medical center where he was employed. His course was complicated by pneumonia, respiratory failure, and encephalitis, but he recovered after treatment with intravenous immune globulin and ribavirin.

Two measles-associated deaths occurred for a reported death-to-case ratio of 5.6/1000 cases. One death occurred in an 8-month-old infant, the other in a 23- month-old unvaccinated child. Both patients had nosocomially acquired cases and were exposed to measles while hospitalized for other illnesses.

On July 21, the Los Angeles County Department of Health Services lowered the minimum age for measles vaccination to 12 months. Media announcements informed the public of measles transmission in Los Angeles County, and parents were urged to have their children vaccinated. The health department also recommended that 1) medical facilities, including emergency rooms (ERs), vaccinate measles-susceptible patients between 12 months and 4 years of age seen for any reason, unless a valid contraindication to vaccination exists; 2) ER staff promptly screen patients and isolate those suspected of having measles; and 3) medical staff without evidence of immunity to measles and who have patient contact be vaccinated. Reported by: G Lentini, P Heseltine, MD, Los Angeles County/Univ of Southern California Medical Center, Los Angeles; J Amling, E Evashwick, Childrens' Hospital, Los Angeles; E Smith, Kaiser-Bellflower Hospital, Bellflower; SH Waterman, MD, PD Frederick, MPH, County of Los Angeles Dept of Health Svcs; L Dales, MD, D Lyman, MD, State Epidemiologist, California Dept of Health Svcs. Div of Immunization, Center for Prevention Svcs, CDC.

Editorial Note

Editorial Note: Measles transmission in preschool-aged children remains a major impediment to elimination of measles in the United States (2). Measles epidemiology in Los Angeles County is similar to that of other recent inner-city measles outbreaks among preschoolers in low socioeconomic groups in which most affected persons were unvaccinated (2-4). To improve vaccine coverage in high-risk children less than 15 months of age, the Immunization Practices Advisory Committee (ACIP) recently recommended that public health officials in areas with recurrent measles transmission lower the minimum age for routine vaccination to 9 months of age (5). Children vaccinated before their first birthday should receive single-antigen measles vaccine and be revaccinated with measles, mumps, and rubella vaccine (MMR) at 15 months of age. An alternate strategy is to lower the age for routine vaccination to 12 months using one dose of MMR.

Lowering the minimum age for vaccination is an important adjunct to control measles transmission among children younger than the routine age for vaccination. However, the large percentage (77.8%) of vaccine-eligible patients 16 months to 4 years of age who were unvaccinated demonstrates the need for intensive efforts to increase vaccine coverage in this hard-to-reach group. Thus, long-term outreach programs are needed for parents and children in low socioeconomic groups in urban areas. Programs should emphasize the following: Barriers to obtaining immunizations (e.g., physical or sociocultural) should be minimized, for example, by providing vaccination clinics on weekends and during evening hours convenient to families needing these services; Local community leaders and health officials should collaborate to promote age-appropriate vaccinations and use of existing public health systems; Community settings, such as church groups, schools, and mobile vans in neighborhoods, should be considered for vaccine delivery and health education programs. Such outreach efforts may improve vaccination levels, decrease measles transmission, and promote regular preventive health care. In Los Angeles County and other areas with recent measles outbreaks in the United States, multiple settings of transmission have been identified (2-4). Exposure to measles in medical settings has been important in perpetuating measles transmission (2-4,6). While most of the transmission in medical settings involved preschool- aged children, medical personnel have also been affected. The ACIP recommends that hospitals and other medical facilities ensure that personnel at risk for occupational exposure to measles be immune (7). A survey conducted in 1985-86 indicated that only eight of the 147 acute-care hospitals in Los Angeles County had mandatory policies requiring employees to provide documentation of measles immunity (Immunization Unit, California Department of Health Services, unpublished data). In Los Angeles County, three medical centers reported nearly half (169) of the 355 measles cases with onset from May 1 to December 31, 1988, including one center that accounted for more than one fourth (96) of all cases. Two of these centers have instituted policies for employees at risk for exposure to measles.

The risk for measles transmission was even more likely to be high in Los Angeles County because the inner-city Hispanic community (which was the major focus of this outbreak) seeks routine medical care primarily through hospital ERs, as demonstrated by the number of patients with measles seen in ERs. In addition to increasing vaccination coverage in this hard-to-reach group, vaccinating in ERs may help curtail transmission in these settings. However, in Los Angeles County, programmatic constraints have precluded vaccination of susceptible, vaccine-eligible children in most ERs. Transmission in ERs may also be reduced by prompt screening of patients and isolation of those suspected of having measles, a difficult task since measles patients are infectious during the prodrome of their illnesses before the appearance of rash. This control measure was implemented in hospital ERs in Los Angeles County.

Measles transmission in Los Angeles County also occurred among school-aged persons, another major pattern of transmission in the United States (2,8). During a 5-week period in the fall, 47 students and employees at a university in Los Angeles developed measles. As a result of efforts by the state and county health departments, more than 3700 of the estimated 20,000 students at the university were vaccinated at special on-campus clinics. In addition, officials from the health departments urged the university and all other Los Angeles County colleges and universities to require documentation of both measles and rubella immunity as a prerequisite to matriculation, a recommendation supported by the ACIP (7) and the American College Health Association (9).

References

1. CDC. Classification of measles cases and categorization of measles elimination programs. MMWR 1983;31:707-11. 2.Markowitz LE, Preblud SR, Orenstein WA, et al. Patterns of transmission in measles outbreaks in the United States, 1985-1986. N Engl J Med 1989;320:75-81. 3.CDC. Measles--New Jersey. MMWR 1986;35:213-5. 4.CDC. Measles--Dade County, Florida. MMWR 1987;36:45-8. 5.ACIP. Measles prevention: supplementary statement. MMWR 1989;38:11-4. 6.Davis RM, Orenstein WA, Frank JA Jr, et al. Transmission of measles in medical settings, 1980 through 1984. JAMA 1986;255:1295-8. 7.ACIP. Measles prevention. MMWR 1987;36:409-18,423-5. 8.Williams WW, Markowitz LE, Cochi SL, et al. Immunizations in college health: the remaining tasks. J Am Coll Health 1987;35:252-60. 9.American College Health Association. Position statement on immunization policy. J Am Coll Health 1983;32:7-8. *According to the CDC classification, a case is considered preventable if measles illness occurs in a U.S. citizen 1) at least 16 months of age, 2) born after 1956, 3) lacking adequate evidence of immunity to measles (documented receipt of live measles vaccine on or after the first birthday, or physician-diagnosed measles disease), 4) without a medical contraindication to receiving vaccine, and 5) with no religious or philosophic exemption under state law (1).

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