Epidemiologic Notes and Reports Measles -- United States, First 26 Weeks, 1987
For the first 26 weeks of 1987, a provisional total of 2,637 measles cases was reported to CDC by 37 states and 5.6% of the nation's 3,138 counties.* This total is 32.7% less than the 3,921 cases reported for the same period in 1986 (1), when 42 states and 9.0% of the counties reported cases. The overall incidence rate for the first half of 1987 was 1.1 cases per 100,000 population; the rate for the first half of 1986 was 1.7/100,000.
Seven states and New York City accounted for 2,148 (81.5%) of the cases reported for the first 26 weeks of 1987: California reported 647; New York City, 414; New Mexico, 303; Texas, 200; Missouri, 178; New Hampshire, 150; Wisconsin, 139; and Illinois, 117. Incidence rates greater than 3.0/100,000 occurred in New Mexico (22.8), Montana (15.6), New Hampshire (13.2), New York City (5.1), Delaware (4.5), Vermont (4.1), and Missouri (3.6).
CDC's Division of Immunization received detailed information on 2,595 (98.4%) of the 2,637 reported cases. Of these, 2,305 (88.8%) met the standard clinical case definition for measles,** and 723 (27.9%) were serologically confirmed. The usual seasonal pattern was observed--most cases occurred between March and May (weeks 9 to 19) (Figure 1).
Fifty-seven (2.2%) of the 2,595 cases were known to be imported from other countries; 30 (52.6%) of these cases occurred among U.S. citizens. An additional 74 cases (2.9%) were epidemiologically linked to imported cases within two generations. Forty-six outbreaks (five or more epidemiologically related cases) accounted for 87.6% of all cases. Five outbreaks of more than 100 cases each accounted for 59.2% of all reported cases.
As in 1986, almost 30% of cases involved children under 5 years of age (Table 1). Two hundred twenty-five (30.0%) of the 750 preschool-aged patients were less than 1 year of age; 122 (16.3%) were 12-14 months of age; 32 (4.2%), 15 months of age; and 371 (49.5%), 16 months through 4 years of age. The 15- to 19-year age group also accounted for approximately 30% of the cases and was the only age group for which the incidence rate did not decrease between 1986 and 1987. The groups aged zero to 4 years and 15-19 years had the highest incidence rates (4.1/100,000 each); the 10- to 14-year age group had the next highest (3.0/100,000).
Complications were reported in 351 (13.5%) of the 2,595 cases. Otitis media was reported in 175 (6.7%) cases; diarrhea, in 129 (5.0%); pneumonia, in 68 (2.6%); and encephalitis, in 2 (0.1%). Two hundred and one (7.7%) of these patients were hospitalized. Four deaths were attributed to measles, for a death-to-case ratio of 1.5:1,000. All four patients were immunocompromised. Two were 4-year-olds with acquired immunodeficiency syndrome; one was a 9-year-old who had autoimmune hemolytic anemia and was receiving corticosteroid therapy; and one was a 57-year- old with chronic lymphocytic leukemia. Two cases were acquired in the hospital, and two were acquired in the community.
Of the 1,805 (69.6%) patients for whom setting of transmission was reported, 960 (53.2%) acquired measles in primary or secondary schools; 122 (6.8%), in colleges or universities; 386 (21.4%), at home; 114 (6.3%), in medical settings; 31 (1.7%), in day-care centers; and 192 (10.6%), in a variety of other settings including work, church, and the military.
A total of 1,274 (49.1%) patients had been vaccinated on or after their first birthdays. This group included 427 (33.5%) who were vaccinated at 12-14 months of age.*** There were 1,213 (46.7%) unvaccinated patients and 108 (4.2%) with histories of vaccination before their first birthdays.
Of the 2,595 cases, 704 (27.1%) were classified as preventable (2), and 1,891 (72.9%), as nonpreventable (Tables 2, 3). Between 1986 and 1987, the absolute number and proportion of preventable cases decreased for all except the over 25-year age group. The highest proportion of preventable cases occurred among persons not of school age--87.5% of cases among adults 25-29 years of age and 68.2% of cases among children 16 months through 4 years of age were preventable. Two hundred sixty-six (37.8%) of the total number of preventable cases involved children 5-19 years of age, and 17.8% of the total cases in this age group were preventable. Cases among adequately vaccinated persons constituted 67.0% of nonpreventable cases and 48.8% of total cases (Table 3). Of the 1,497 school-aged children who acquired measles, 1,119 (74.7%) had been adequately vaccinated, and 406 (27.1%) had been vaccinated at 12-14 months of age. Reported by: Div of Immunization, Center for Prevention Svcs, CDC.
Editorial Note: After the record low of 1,497 measles cases in 1983, the number of measles cases increased each year through 1986. The number of cases reported for the first 26 weeks of 1987 is less than that reported during the comparable period in 1986 and reverses this trend. The incidence rates have decreased in all except the 15- to 19-year age group. The increase in this group was attributable to several large outbreaks in secondary schools and colleges.
The four deaths due to measles during the first half of 1987 are the first reported to the Division of Immunization since 1985 (3). All four cases either initiated or were part of nosocomial outbreaks involving medical personnel. In addition, a higher proportion of cases were acquired in medical settings in 1987 than in previous years (4-6). The deaths, combined with the increased proportion of cases acquired in medical settings, highlight the role of these settings in the transmission of measles and emphasize the need for immunization requirements for medical personnel at risk of exposure (7,8).
As in previous years, a large proportion of persons who acquired measles had been vaccinated. In an effort to decrease the occurrence of these cases, changes in the current immunization strategy are being discussed. In many outbreaks, persons vaccinated at 12-14 months of age have been demonstrated to be at slightly higher risk for measles than persons vaccinated at 15 or more months of age. Therefore, the Immunization Practices Advisory Committee (ACIP) recently recommended that revaccination of persons previously vaccinated at 12-14 months of age be considered during outbreaks (8,9). Most cases of measles among persons who received vaccine at 15 months of age or older appear to be the result of primary vaccine failure and not of waning immunity (10).
The two major impediments to measles elimination in the United States-- unvaccinated preschoolers and vaccine failure in the school-aged population-- require different solutions. Health-care providers should take advantage of every opportunity to vaccinate these children (11). Measles-containing vaccines should be administered to eligible children regardless of the need for other vaccines. The ACIP now recommends simultaneous administration of MMR, DTP, and OPV at 15 months of age (12), both routinely and for children behind on their immunization schedules.
The number of vaccine failures among children 5-19 years of age has stimulated efforts to devise strategies to reduce the rate of primary vaccine failure. CDC is convening a group of consultants to review the current status of efforts to eliminate measles in the United States and to discuss potential modifications (13) to the current strategies. These modifications include revaccination, either routinely, as a two-dose schedule, or selectively, as part of outbreak control.
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