Measles -- Dade County, Florida

During the period July 14 through December 12, 1986, 258 confirmed cases of measles (1) were reported to the Dade County Department of Public Health. There is detailed information available on the first 223 cases, all of which had been reported by December 6, 1986 (Figure 1). The index case of measles occurred in a 4-year-old, unvaccinated Hispanic resident of Dade County. The child had acquired measles while on vacation in Honduras, and her rash had developed on June 19, the day after she returned home.

Of the 223 patients reported to Dade County, 98 (44%) were black; 76 (34%), Hispanic; 28 (13%), Haitian; and 21 (9%), non-Hispanic white. Attack rates were highest among blacks (43 cases/100,000 population) and Haitians (32/100,000), with lower attack rates among Hispanics (10/100,000) and whites (6/100,000). The age distribution of the 223 patients is presented in Table 1. A total of 171 (77%) were 5 years of age; 91 (41%) were 16 months of age (i.e., too young for routine vaccination). The highest attack rate (248/100,000) was in patients 12 months of age (Table 1).

Overall, 39% (87) of the 223 patients had preventable illness (1) (Table 2). However, 89% (71) of cases in preschoolers who were 16 months through 4 years of age were preventable. This age group alone accounted for 82% of all preventable cases (Table 2). Of the 136 children who had non-preventable cases, 91 (67%) were too young for routine vaccination, 42 (31%) had been vaccinated, two (2%) were born before 1957 (i.e., old enough to be considered already immune), and one (0.7%) was not a U.S. citizen.

Complications occurred in 77 (32%) of the 223 patients. The most frequent complication was diarrhea (14%), followed by otitis media (10%), pneumonia (6%), and seizures (1%). Age-specific complication-to-case ratios were highest among children 5 years of age (44:172); the 9- to 15-month age group had the highest ratio (24:73). No deaths were reported.

The setting of transmission was known for 79 (35%) patients. Of these patients, 42 (53%) were exposed to measles in the waiting room of the pediatric emergency room (ER) of a large county hospital. Transmission also occurred in other medical facilities, day-care centers, shelters for children, homes, and schools where immunization levels were known to be high (98%).

Outbreak control activities included increasing surveillance; instituting mass publicity in newspapers, on radio and television stations, and by physicians and other health professionals; instituting a triage and isolation process in the pediatric ER and clinics of the county hospital; and auditing records of children enrolled in licensed day-care centers and schools. On September 25, the age of vaccination was lowered to 12 months. On October 17, because of continuously high attack rates in infants 12 months, the age of vaccination was lowered to 6 months for children either living in shelters or using neighborhood clinics or the pediatric ER of the county hospital. Free vaccine was provided in all neighborhood and public health clinics. In neighborhoods where large proportions of patients lived, religious and other community leaders assisted in vaccine clinics held in mobile vans, churches, fleamarkets, and supermarkets. Vaccine was also available in a van outside of the pediatric ER of the county hospital. However, these clinics had limited success in immunizing preschoolers.

Because a large proportion of patients was unvaccinated, a telephone survey was conducted to determine whether patients had missed an opportunity to be vaccinated and what the risk factors were for not being immunized. To determine missed opportunities for vaccination, parents or guardians of 18 unvaccinated patients who were 16 months through 4 years of age were interviewed to determine the number of times they were seen in a medical care facility at an age when they were eligible for vaccination. Of the 18, 17 had reportedly been seen in a medical care facility at least one time in the 6-month and 12-month periods prior to measles onset and at an age when they were eligible for vaccination. Review of the clinical records of nine patients indicated that three had been seen for minor upper respiratory tract infections and could have received vaccine. The remaining six were seen when they had an illness which was felt to be a contraindication to vaccination.

To determine the risk factors for not being immunized, a case-control study was conducted. The 18 unvaccinated patients who were 16 months through 4 years of age were compared with 27 community controls in the same age group. The control group was obtained by random digit dialing. Preliminary results of this case-control study indicated that unvaccinated patients were more likely to have received health care from the public sector (odds ratio (OR) = 10, 95% confidence interval (CI) = 2-40), to have single mothers (OR = 13, 95% CI = 3-58), to live in a household with no employed adult (OR = 7, 95% CI = 2-26), to have received 3 doses of DTP = (p = 0.016*) and 2 doses of OPV** (p = 0.048*). They also had a greater number of siblings (mean = 2 vs 1, p 0.05). Reported by M Ares, MD, H Garcia, MD, A Kimbler, RA Morgan, MD, Dade County Dept of Public Health, HT Janowski, H Loy, S McInelly, JL Velez, JJ Witte, MD, MH Wilder, MD, Acting State Epidemiologist, Florida State Dept of Health and Rehabilitative Svcs; Div of Immunization, Center for Prevention Svcs, CDC.

Editorial Note

Editorial Note: Measles transmission in preschool-aged children continues to be a major impediment to the elimination of indigenous measles transmission in the United States. Preschoolers have had the highest reported risk of measles among all age groups in 5 of the 6 years from 1981 through 1986 (2,3). Unvaccinated preschoolers aged 16 months through 4 years represent a substantial proportion of patients in recent outbreaks in Phoenix (4), Chicago (5), Jersey City (6), and New York City (CDC, unpublished data). As in those outbreaks, the outbreak in Dade County occurred among preschoolers from low socioeconomic groups.

Generally, immunization levels in preschool-aged children are lower than those for school-aged children (6,7). This is true in Dade County where a survey of 2-year-old children in the population in 1986 showed that the measles immunization level was between 49% and 65% (Dade County Department of Public Health, unpublished data). In contrast, the immunization level in children enrolled in kindergarten and first grade in the 1985-86 school year was 94%.

In the outbreak in Dade County, unvaccinated patients were of lower socioeconomic status, sought health care more often in the public sector, and were more likely not to be in compliance with immunization recommendations for other antigens than were their age-matched controls. These children are particularly difficult to reach for several reasons. In addition to not being enrolled in schools or some other institution where immunization requirements could be enforced, they may also have difficulty gaining access to health care services. There is a need for innovative strategies for increasing immunization levels among this hard-to-reach group throughout the United States. Barriers to immunization services should be eliminated, and the services available in public health clinics, where these patients usually seek care, should be more fully used. In addition, susceptible children should be vaccinated every time they visit a health care facility unless vaccination is contraindicated. Educational programs should be targeted to parents in low socioeconomic groups, and physicians and clinics should routinely recall their eligible patients for vaccination. The health care community should involve community leaders in planning activities to educate parents.

References

1. CDC. Classification of measles cases and categorization of measles elimination programs. MMWR 1983;31:707-11.

2. Frank JA Jr, Orenstein WA, Bart KJ, et al. Major impediments to measles elimination. Am J Dis Child 1985;139:881-8.

3. CDC. Measles--United States, first 26 weeks, 1986. MMWR 1986;35:525-8, 533.

4. CDC. Measles--Arizona. MMWR 1986;35:99-100, 105-7.

5. Bennish M, Arnow PM, Beem MO, Doveikis S. Epidemic measles in Chicago in 1983: sustained transmission in the preschool population. Am J Dis Child 1986;140:341-4.

6. CDC. Measles--New Jersey. MMWR 1986;35:213-5.

7. Eddins DL, Sirotkin BI, Holmgreen P, Russell S. Assessment and validation of immunization status in the United States. In: 20th Immunization Conference Proceedings. Dallas, Texas: 20th Immunization Conference, 1985:51-61. *Odds ratio not calculated; zero value in one cell.

At least two doses of OPV and three doses of DTP are recommended by 15 months of age.

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