AMERICAN ACADEMY OF PEDIATRICS. Measles: Reassessment of the Current Immunization Policy. Commiftee on Infectious Diseases

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1 AMERICAN ACADEMY OF PEDIATRICS Commiftee on Infectious Diseases Measles: Reassessment of the Current Immunization Policy Since the licensure of measles vaccine in the United States a quarter of a century ago, the number of measles cases has declined by 98% to 99%. Since 1981 the number of cases of rubeola reported annually in the United States has averaged about 3. In 1986, however, 6282 cases were reported, the highest number since 198, and the incidence was 2.7 cases per 1 population, compared with 1.2 the year before. In the subsequent year, 1987, the rate decreased to 1.5 cases per 1 population, which was, nevertheless, the second highest rate since 198. This swell of activity was widespread, with cases reported from 46 states in 1986 and 41 states in In 1988, the measles activity continued with a rate of 1.3 per 1 population. In 1989, the situation worsened, with the Centers for Disease Control having received (as of the end of April) reports of 56 outbreaks which account for more than a 3% increase in cases over the number reported during the similar period of More than half of cases have occurred in those older than 1 years of age. Among those outbreaks, 32% have been in college students, attending schools in 11 states and involving 71 colleges with at least one suspected case of measles. Analysis of these recent cases by the Centers for Disease Control has revealed that the majority (about two thirds) were not preventable by our current policy (Figure). In 1985 and 1986 (the most recent years analyzed), most of these nonpreventable cases occurred in persons who either had been appropriately immunized (6%) or in children who The recommendations in this statement do not indicate an exclusive course of treatment to be followed. Variations, taking into account individual circumstances, may be appropriate. Reprint requests to Publications Department, American Academy of Pediatrics, 141 Northwest Point Blvd, P Box 927, Elk Grove Village, IL PEDIATRICS (ISSN 31 45). Copyright 1989 by the American Academy of Pediatrics. were not old enough to receive routine vaccination at 15 months of age (27%) (Table). Furthermore, the outbreaks could be categorized into two major types: those in preschool-aged children (younger than 5 years of age), which were theoretically preventable because cases occurred in children old enough to have been vaccinated, and those in school- and college-aged persons, primarily 5 to 19 years of age, which were not preventable by current policy, because almost all school-aged children had been previously vaccinated. In 1985 and 1986, 11 outbreaks (67%) primarily occurred among schoolaged children. In contrast to the outbreaks in preschool-aged children, only 27% of these cases were considered preventable, occurring in unvaccinated children. The outbreaks developed in schools in which the immunization rate was usually 96% or more and in which there were characteristically low attack rates of 1% to 5%#{149}157 Of cases occurring in vaccinated children, 8% have been in those older than 12 years of age. The highest age-specific attack rate in recent years, however, has been in preschool-aged chilthen. In 1985 and 1986, 81% ofthe preschool cases that occurred in children who were eligible to receive the vaccine were unimmunized and, thus, were preventable cases. Surveys conducted by the Centers for Disease Control have indicated that as few as 49% to 65% of 2-year-old children in poor urban areas of the United States are immunized.3 The number of cases occurring in children younger than 15 months (the recommended age for immunization) was also appreciable (Figure). Whether infants are more susceptible in recent years because of an earlier decline in their maternal antibody, now induced by vaccine rather than by natural infection, is currently unclear.8 9 If such is shown, the age for routine initial immunization may need to be reduced for all children from 15 months to a younger age, such as 12 months. Downloaded from by guest on March 11, PEDIATRICS Vol. 84 No. 6 December 1989

2 U, C) I, <l6mos. l6mos..4yr. 2 yr. Preventable Cases U Non-preventable Cases Percent of Total Cases of Measles, 1985 and 1986 Figure. Age distribution and proportion of preventable and nonpreventable cases of confirmed measles in United States, 1985 through 1986, analyzed by Centers for Disease Control (adapted from Markowitz et al ). The following recommendations have been devised to increase immunization of the unvaccinated preschool-aged child in high-risk areas and to prevent the spread of measles in schools and colleges by administration of routine second doses later in the life of all children. This second dose is expected to reduce the pool of individuals who have had an ; inadequate response to the initial vaccination, who have had no previous immunization, or who have had an undocumented vaccination. Until all schoolaged children have received revaccination, programs for outbreak control and routine college entry vaccination are necessary. TABLE. Classification of Nonpreventable Measles Cases in the United States from 1985 Through 1986* % of Nonpreventable Cases Appropriately vaccinatedt 6 <l6moofage 27 Exemptions 6 Born before Imported (not US citizen) 2 * From Markowitz. t Documented history of vaccination at 12 months of age. The following observations and possible reasons for this recrudescence of measles are suggested by the investigation of these outbreaks by the Centers for Disease Control: (1) the immunization rate in preschool children (older than 15 months of age) in some areas is low; (2) during outbreaks among young, unimmunized children, infection develops in a sizable proportion of infants who are younger than the recommended age for immunization (15 months); (3) even in schools with high immunization rates (96%), outbreaks may occur, and most cases have occurred in previously immunized children; (4) a proportion ofvaccinees, estimated at 2% to 1%, appeared to have failed to respond adequately to the initial measles immunization given at the appropriate age of 15 months5 #{176}or have lost immunity. Evidence for waning of immunity after vaccination is scant However, well-documented cases of measles have been reported in prior seroconverters 2 and loss of immunity by only a few percent of vaccinees would add substantial numbers to the pool of susceptibles; (5) persons who had been immunized at 12 to 14 months of age (perhaps in the presence of maternal antibodies induced by natural infection) had, in some outbreaks, an increased risk of becoming infected 3; and (6) in persons immunized before 198, a factor possibly contributing to vaccine failure was the greater lability of the measles vaccine manufactured before a new stabilizer was added in RECOMMENDATIONS Routine Vaccination The Committee recommends two doses of measles vaccine for all children after their first birthday. In routine circumstances, the first dose should be given as measles, mumps, and rubella vaccine (MMR) at age 15 months and the second also as MMR at entrance to middle school or junior high school (approximately age 11 to 12 years). Revaccination at this age appears desirable to (1) achieve rapid impact, because the risk of measles increases substantially soon after entrance to middie school or junior high school, (2) boost immunity soon before the high-risk period, and (3) reinforce possible waning immunity. This recommendation can easily be accomplished within the existing schedule for health maintenance visits as described in the AAP s Guidelines for Health Supervision. 4 Some public health jurisdictions may mandate revaccination at the time of school entry (age 5 years), for reasons offeasibility and ease of enforcement, particularly in the public sector. In those areas, physicians must conform to local requirements, but in the interval required for those chilthen to reach the sixth grade, revaccination can also be offered to older children who are closer to the period of recurrent risk, ie, junior high school, high school, and college. However, those physicians who choose to revaccinate earlier in life need not give third doses later when children enter middle school if the first two doses were administered after 12 months of age and were separated by at least 1 month. As additional immunologic information emerges concerning the optimal age for revaccination, this recommendation may be modified. A second dose of measles-containing vaccine is also required for those children who received killed vaccine originally but who were subsequently given live vaccine. Downloaded from PEDIATRICS by guest Vol. on March 84 No. 11, December

3 MMR is recommended over monovalent measles vaccine for revaccination to provide additional immunization against mumps and rubella. Recently, there has been an increase of cases of mumps in persons with histories of prior mumps vaccination. Monovalent measles vaccine may be substituted for MMR by the pediatrician if cost is a factor or for reasons of preference. No unusual reactions have been associated with measles or MMR revaccination. The anticipated side effects are those of the individual vaccines but are expected to be infrequent, as most vaccinees will be immune. Preschool-aged Children in Areas With Recurrent Measles Transmission A large percentage of reported cases and large outbreaks continue to occur in unvaccinated preschool-aged children, often from disadvantaged families living in urban areas. Major efforts need to be directed toward increasing vaccination levels in these areas. Vaccination at 12 months of age is recommended for preschool-aged children in high-risk areas. Guidelines for defining such high-risk areas are (1) a county with more than five cases among preschool-aged children during each of the last 5 years, (2) a county with a recent outbreak among unvaccinated preschool-aged children, and (3) cities with large unvaccinated populations. This strategy assumes that the benefit of preventing measles cases that might occur at 12 to 14 months of age in a high-risk area outweighs the possible lower efficacy of the vaccine when given at this age. During an outbreak in these areas, particularly if there are high attack rates in younger infants, monovalent measles vaccine (MMR) may be given to infants as young as 6 months of age. Children vaccinated before the first birthday should have a repeat vaccination at 15 months of age using MMR vaccine and a third dose at the time of entry to junior high or middle school. Outbreaks in Schools Revaccination. During outbreaks in elementary, junior high, or senior high schools, a program of revaccination is recommended with MMR vaccine in both the affected schools and unaffected schools at high risk of measles transmission. Revaccination should include all students and their siblings born after January 1, 1957, who have not received two doses of measles-containing vaccines after 12 months of age. Persons born before 1957 likely would have been exposed to natural measles virus, unrestricted by the epidemiologic inpact of the vaccine. Immunization After Expose. Measles containing vaccine adminsistered within 72 hours of exposure should prevent the disease and is recommended for the exposed child. Infants younger than 1 year of age may be given immune globulin as an alternative and vaccinated several months later. Quarantine. Imposition of quarantine measures is both logistically difficult and disruptive to schools and other organizations. Although unusual circumstances may warrant restriction of events, the Committee does not recommend this as a routine measure for outbreak control. Colleges and Other Institutions Colleges, vocational and technical schools, graduate schools, and other institutions for education beyond high school should require documentation of measles or receipt of two doses of measles-contaming vaccines before entry of all students. If there is no documentation of any measles vaccination, a dose can be given at entry and repeated 1 or more months later. Medical Facilities Evidence of prior measles or receipt of two measles vaccinations is desirable before beginning employment of nurses, nursing and medical students, residents, and other staff born after January 1, If an outbreak occurs in the areas served by the hospital, all employees with patient contact born after that date who do not have a documented history of measles, an antibody titer indicative of immunity, or documentation of two prior doses of measles vaccine should receive an additional dose. Contraindications Pregnancy or immunosuppression are contraindications to vaccination. Live measles vaccine should not be given to women known to be pregnant or who are considering becoming pregnant within 3 months of vaccination. This precaution is based on the theoretical risk of fetal infection which applies to the administration of any live virus vaccine to women who might be pregnant or who might become pregnant soon after vaccination. No evidence substantiates this theoretical risk. Protection of adolescents and young adults against measles and its known serious risks is important; therefore, asking women whether they are pregnant, excluding those who are, and explaining the theoretical risks to the others are recommended precautions in a measles immunization program. C 1112 MEASLES Downloaded IMMUNIZATION from POLICY by guest on March 11, 219

4 Research Needs The changing epidemiology of measles in the United States makes continual reassessment of the C current vaccine policy necessary. Research is urgently needed concerning the factors that influence the circulation of measles virus, the persistence of immunity, the efficacy of revaccination, and measles vaccine strains with possible improved efficacy. Recommendations may change in the future as new information becomes available. CMMrrrEE ON INFECTIOUS DISEASES, Stanley A. Plotkin, MD, Chairman Robert S. Daum, MD G. Scott Giebink, MD Caroline B. Hall, MD Martha Lepow, MD Edgar K. Marcuse, MD George H. McCracken, Jr, MD Carol F. Phillips, MD Gwendolyn B. Scott, MD Harry T. Wright, Jr, MD Ex-Officio Georges Peter, MD Liaison Representatives Ronald Gold, MD, Canadian Paediatric Society Alan R. Hinman, MD, Centers for Disease Control John R. La Montagne, MD, National Institute of Allergy & Infectious Diseases Paul Parkman, MD, Food and Drug Administration REFERENCES AAP Section Liaison James G. Easton, MD, Section on Allergy and Immunology 1. Markowitz LE, Preblud SR, Orenstein WA, et al. Patterns of transmission in measles outbreaks in the United States, N Engi J Med. 1989;32: Centers for Disease Control. Measles-United States, MMWR. 1987;36: Centers for Disease Control. Measles-Dade County, Florida. MMWR. 1987;36: Preblud SR, Markowitz LE, Orenstein WA. Update on measles vaccine effectiveness. Twenty-first Immunization Conference Proceedings, New Orleans, LA. June 8-li, Orenstein WA, Hinman AR, Preblud SR, et al. Additional strategies for measles elimination. Twenty-first Immunization Conference Proceedings, New Orleans, LA. June 8-il, Gustafson TL, Brunell PA, Lievens AW, et al. Measles outbreak in a fully immunized secondary school population. N Engi J Med. l987;316: Nkowane BM, Bart KJ, Orenstein WA, et al. Measles outbreak in a vaccinated school population. Epidemiology, strains of transmission and the role of vaccine failures. Am J Public Health. 1987;77: Lennon JL, Black FL. Maternally derived measles immunity in an era of vaccine-protected mothers. J Pediatr. 1986;l8:67l Jenks PJ, Caul EO, Roome PCH. Maternally derived measles immunity in children of naturally infected and vaccinated mothers. Epidemwl Infect. 1988;l1: Frank JA, Orenstein WA, Bart KJ, et al. Major impediments to measles elimination: the modern epidemiology of an ancient disease. Am J Dis Child. 1985;139: Mathias RG, Meekison WG, Arcand TA, et al. The role of secondary vaccine failures in measles outbreaks. Am J Public Health. 1989;79: Zhuji Measles Vaccine Study Group. Epidemiologic examination of immunity period of measles vaccine. China Med J. 1987;67: Orenstein WA, Markowitz LE, Preblud SR, et al. Appropriate age for measles vaccination in the United States. Dev Biol Stand. 1986;65: Committee on Psychosocial Aspects of Child and Family Health. Guidelines for Health Supervision II. Elk Grove Vi&zge, IL: American Academy ofpediatrics; 1988 Downloaded from AMERICAN by guest ACADEMY on March 11, OF 219 PEDIATRICS 1113

5 Measles: Reassessment of the Current Immunization Policy Pediatrics 1989;84;111 Updated Information & Services Permissions & Licensing Reprints including high resolution figures, can be found at: Information about reproducing this article in parts (figures, tables) or in its entirety can be found online at: Information about ordering reprints can be found online: Downloaded from by guest on March 11, 219

6 Measles: Reassessment of the Current Immunization Policy Pediatrics 1989;84;111 The online version of this article, along with updated information and services, is located on the World Wide Web at: Pediatrics is the official journal of the American Academy of Pediatrics. A monthly publication, it has been published continuously since Pediatrics is owned, published, and trademarked by the American Academy of Pediatrics, 141 Northwest Point Boulevard, Elk Grove Village, Illinois, 67. Copyright 1989 by the American Academy of Pediatrics. All rights reserved. Print ISSN: Downloaded from by guest on March 11, 219