Measles -- United States, 1992

As of January 2, 1993 (week 53), local and state health departments reported a provisional total of 2200 * measles cases for 1992 (1) -- a 77% decrease from the 9643 cases reported for 1991 (2), and a 92% decrease from the 27,786 cases reported for 1990 (3). Cases were reported from 36 states and the District of Columbia. This provisional total is one of the lowest annual totals reported in the United States; fewer cases were reported only in 1982 (1714 cases) and 1983 (1497 cases) (4). This report summarizes epidemiologic characteristics of measles cases reported for 1992 and compares them with cases reported during 1989-1991.

From 1989 through 1992, the median age of persons reported with measles declined steadily (12.0 years in 1989, 5.7 years in 1990, 5.2 years in 1991, and 4.9 years in 1992), while the proportion of cases among infants increased. Of measles cases in 1992, 22.2% occurred among children less than 12 months of age, an increase from 19.2% in 1991 and 17.0% in 1990; 27.9% of reported cases were among children aged 1-4 years, compared with 30.1% for 1991. Persons aged greater than or equal to 5 years accounted for 49.7% of reported cases, compared with 50.6% in 1991. A provisional total of three measles-associated deaths was reported in 1992 for Texas (two) and Alaska (one).

Texas and Kentucky reported the largest outbreaks (990 and 443 cases, respectively) during 1992. The outbreak in Texas continued the pattern of outbreaks reported during 1989-1991 affecting predominantly unvaccinated preschool-aged children (2,3 ). Seventy-one percent of cases in this outbreak were reported from Nueces and Hidalgo counties; the other cases were reported from 22 (9%) of 254 counties in the state. Most (75%) cases were among children aged less than 5 years; 35% of cases were among children less than 12 months of age. In comparison, in Kentucky, measles transmission occurred predominantly among children aged 5-19 years (218 cases {49%}). Fifty-one percent of cases from the Kentucky outbreak were reported from Jefferson County (Louisville); the remaining cases were reported from 34 (28%) of 120 counties in the state.

Reported by: State and local health depts. Div of Immunization, National Center for Prevention Svcs, CDC.

Editorial Note

Editorial Note: During 1989-1991, a period of increased measles transmission, approximately 55,000 cases and 132 suspected measles-associated deaths were reported. However, from mid-October 1992 through January 1993, no outbreaks of measles (i.e., five or more epidemiologically related cases) were reported, suggesting that the measles resurgence in the United States has ended. During the first 18 weeks of 1993, 80 measles cases were reported, representing only 13% of the number reported for the same period during 1992. Possible explanations for the end of the measles resurgence include a decrease in susceptible populations following widespread transmission of the virus; improved vaccination coverage in the susceptible population; an overall decrease in the occurrence of measles in the Western Hemisphere (5); and the periodic cyclicity in measles transmission that has been noted since the prevaccine era.

The magnitude of the recent resurgence is not likely to have substantially reduced susceptibility (2), even in cities with the highest incidence of measles. For example, retrospective surveys of school enterers in 15 cities indicated that coverage against measles ranged from 51% to 79% at the time of the second birthday (6,7); based on these findings, approximately 800,000-2 million U.S. children aged 12-23 months would be susceptible. However, during 1989-1992, approximately 9300 cases of measles were reported among children aged 12-23 months -- a number insufficient to have substantially reduced overall susceptibility in this age group.

A reduction in measles susceptibility may have occurred through increased measles vaccination levels among preschool-aged children. From 1971 through 1985, the United States Immunization Survey (USIS) demonstrated that measles vaccine coverage among children aged 1-4 years ranged from 61% to 66% (CDC, unpublished data, 1986). By comparison, the National Health Interview Survey (NHIS) in 1991 targeted the same population as the USIS and documented measles vaccine coverage to be 78% among children aged 1-4 years -- the highest level ever reported (CDC, unpublished data, 1993).

The estimates of increased vaccine coverage, based on the NHIS, are consistent with data indicating increased measles vaccine administration in the public sector. During 1991 and 1992, 1,358,117 and 1,344,901 doses, respectively, of measles vaccine were administered in public clinics to children aged 12-23 months -- a 42% and 41% increase, respectively, when compared with 1988 (953,535 doses), the year before the measles resurgence (CDC, unpublished data, 1993). In addition, in 1992, provisional totals of reported mumps (2433) and rubella (147) (1) were the lowest since reporting began in 1968 and 1966, respectively, reflecting the contribution of increased vaccination with combined measles-mumps-rubella (MMR) vaccine.

In contrast to vaccination coverage for measles, mumps, and rubella, coverage against other diseases has not increased substantially. In particular, NHIS findings for 1991 indicated that only 66% of children aged 1-4 years had received three or more doses of diphtheria and tetanus toxoids and pertussis vaccine (DTP), and 51% had received three or more doses of oral poliovirus vaccine (OPV) (Table 1) -- coverage comparable to or lower than that reported in previous years. Overall, only 42% of preschool-aged children had received all age-appropriate vaccinations **, although this level may underestimate coverage because parents may have failed to recall some doses of multiple-dose vaccines (8). However, this level is substantially lower than the national health objective for the year 2000 of 90% complete series coverage by the second birthday (objective 20.11) (9).

Strategies to improve vaccination levels include 1) reducing barriers to vaccination (e.g., increasing the number of clinic hours when vaccinations are given and the availability of walk-in vaccination services); 2) taking advantage of all opportunities to vaccinate (e.g., simultaneous use of multiple vaccines whenever possible, excluding from vaccination only persons with valid contraindications); 3) using innovative vaccine delivery techniques (e.g., vaccination in hospital emergency departments); 4) increasing the number of children who return for vaccination at the appropriate age by improving follow-up and recall systems; and 5) providing education about vaccination to parents (10).

A major comprehensive childhood vaccination initiative is under way to improve levels among preschool-aged children. The principal components of this initiative are 1) improving the vaccine delivery infrastructure through increased federal funding for this purpose (e.g., increasing vaccination clinic personnel and hours of operation, particularly in the inner cities); 2) assuring universal access to vaccination services; and 3) assuring that computerized systems are established in each state for tracking the vaccination status of all children.

To sustain the decrease in transmission of measles in the United States, and to achieve similar results with other vaccine-preventable diseases, age-appropriate vaccination coverage efforts must be improved -- particularly among preschool-aged children living in inner-city areas. Transmission of measles among preschool-aged children is likely to recur unless measles vaccine coverage is improved and age- appropriate vaccination is ensured.

References

1. CDC. Table II. Cases of selected notifiable diseases, United States, weeks ending January 2, 1993, and December 28, 1991 (53rd week). MMWR 1993;41:981.

2. CDC. Measles surveillance -- United States, 1991. In: CDC surveillance summaries (November 20). MMWR 1992;41(no. SS-6):1-12.

3. CDC. Measles -- United States, 1990. MMWR 1991;40:369-72.

4. CDC. Summary of notifiable diseases, United States 1991. MMWR 1992;40(no. 53):57-62.

5. Pan American Health Organization. Reported cases of EPI diseases. EPI Newsletter 1992;14:7.

6. CDC. Measles vaccination levels among selected groups of preschool-aged children -- United States. MMWR 1991;40:36-9.

7. CDC. Retrospective assessment of vaccination coverage among school-aged children -- selected U.S. cities, 1991. MMWR 1992;41:103-7.

8. Valadez JJ, Weld LH. Maternal recall error of child vaccination status in a developing nation. Am J Public Health 1992;82:120-2.

9. Public Health Service. Healthy people 2000: national health promotion and disease prevention objectives. Washington, DC: US Department of Health and Human Services, Public Health Service, 1991; DHHS publication no. (PHS)91-50213:76.

10. CDC. Standards for pediatric immunization practices. Atlanta: US Department of Health and Human Services, Public Health Service, 1993.

• Final totals for measles reported in 1992 will be published later in 1993. ** Up-to-date for age was based on the recommended number of doses of DTP, OPV, and MMR vaccine as recommended by the Advisory Committee on Immunization Practices and the American Academy of Pediatrics plus a 30-day grace period. When the recommendation did not agree, the later recommended age was used.

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