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The effects of measles immunization on immune responses in infants and the roles of vaccine strain and age of immunization are not known. Eighty-eight children were immunized at 6 or 9 months of age with the Edmonston-Zagreb (EZ) or Schwarz (SW6, SW9) strain of measles vaccine. Children were studied before and 2 weeks and 3 months after immunization. Seroconversion was similar, but geometric mean neutralizing titers at 3 months differed by vaccine group: SW9, 1367 mIU/mL; SW6, 982; and EZ, 303 (P = .003). Mitogen-induced lymphoproliferation was decreased at 2 weeks in the SW9 group and at 3 months in all groups and was negatively correlated with measles antibody level at 3 months (r = -.387, P = .003). CD8 T cells, soluble CD8, neopterin, and beta2-microglobulin were increased at 2 weeks in the SW9 group, and soluble CD8 and beta2-microglobulin remained elevated at 3 months. Therefore, measles immunization resulted in suppression of lymphoproliferation, which was most evident in infants with the highest antibody responses and most immune activation.

Background: A two dose measles vaccination schedule is recommended routinely for all school-entry-aged children. We evaluated this recommendation by determining both measles antibody seroprevalence and the response to revaccination in seronegative children in this age group., Methods: Children 4 to 6 years of age who had received a single dose of measles vaccine between the ages of 15 to 17 months were tested for measles antibody by using enzyme-linked immunosorbent assay (ELISA) microneutralization technique. Seronegative children were revaccinated and again tested for measles antibody (immunoglobulin M [IgM] and neutralizing)., Results: Of 679 children tested, 37 (5.4%) were seronegative. Seronegativity was not significantly associated with age, sex, race, age at initial vaccination, time since vaccination, or maternal year of birth. However, children mothers with a college degree were 12 times more likely to be seronegative than children of mothers who never attended college (P < .01). Of the 37 seronegative children, 36 seroconverted after revaccination--33 producing IgM measles antibody, suggestive of a primary immune response. The cost per seroconversion would have been an estimated $415 if all 679 children had been revaccinated., Conclusions: Revaccination reduces the pool of children who are susceptible to measles. Although the cost per seroconversion is high, a two-dose schedule should reduce the substantial costs of controlling measles out breaks by reducing the number of outbreaks.

Objectives: The goals of this study were to evaluate the proportion of previously vaccinated human immunodeficiency virus (HIV) type 1-infected children with detectable postvaccination measles antibody; to assess risk factors for vaccine failure; and to evaluate the response to reimmunization., Methods: A total of 81 perinatally HIV-infected children receiving medical care in the Bronx, New York who had previously received measles vaccine were enrolled. The Centers for Disease Control and Prevention (CDC) HIV class, lymphocyte subsets, and measles antibody were determined upon enrollment. Additional data abstracted from medical records included dates and number of prior measles vaccinations and CDC HIV class at the time of vaccination. Measles antibody was determined by microneutralization enzyme-linked immunosorbent assay (ELISA)., Results: The median age at time of study was 42 months (range, 9 to 168 months). Overall, 58 (72%) subjects had detectable measles antibody (microneutralization ELISA titer > 1:5). Children studied within 1 year of vaccination were more likely to have detectable measles antibody than children evaluated more than 1 year after vaccination (83% vs 52%, P < .01). The proportion of children with detectable measles antibody was higher among children with no or moderate immunosuppression compared to those with severe immunosuppression when immune status was based on CD4%. Children vaccinated at 6 to 11 months of age appeared to have a higher proportion of detectable measles antibody than those who received a first measles vaccination after age 1. Only 1 (14%) of 7 previously vaccinated children who were seronegative or had very low titers experienced a four-fold rise in measles antibody when reimmunized., Conclusion: These results support current recommendations to vaccinate HIV-infected children against measles. The proportion of children with detectable measles antibody among vaccinated HIV-infected children is considerably lower than in vaccinated healthy children. HIV-infected children may respond better to measles vaccine when it is administered before the first birthday. From our limited data it appears that reimmunization of previously vaccinated HIV-infected children with moderate to severe immunosuppression does not result in an antibody recall response.

Objective: To examine the response to measles-mumps-rubella (MMR) vaccine among children with and without mild illness., Design: Prospective cohort., Participants: A total of 386 children aged 15 to 23 months., Main Outcome Measures: Seroconversion rates to measles, mumps, and rubella in ill and well children., Setting: Six public health immunization clinics in two counties in the greater metropolitan Atlanta, Ga, area from February 1992 to April 1993., Results: Acute upper respiratory tract infection, otitis media, and diarrhea were observed in 128 (33%), 41 (11%), and 13 (3%) of the children (groups are not mutually exclusive); 157 children had one of these mild illnesses and 229 were well. Overall seroconversion rates were 98% for measles, 83% for mumps, and 98% for rubella antigens. Measles seroconversion rates for ill children compared with well children, respectively, were as follows: upper respiratory tract infection, 99% vs 97%; mild fever, 98% vs 97%; otitis media, 98% vs 98%; diarrhea, 100% vs 98%; and any mild illness, 99% vs 97%. Estimates of the magnitude of antibody response to measles, mumps, and rubella antigens were the same for children with and without mild illness. There was no association of mild illness with increased rates and severity of adverse events reported in the 2 weeks after vaccination., Conclusions: Vaccinating children who present with mild illnesses with MMR vaccine is a safe and efficacious practice. These results support recommendations of the Advisory Committee on Immunization Practices and the American Academy of Pediatrics.

Objectives: In the United States, younger women are more likely to have immunity to measles from vaccination and are less likely to have been exposed to the wild virus than are older women. To evaluate changes in measles antibody titers in women in the United States and children's responses to measles vaccination, we analyzed data from a measles vaccine trial., Methods: Sera collected from children before vaccination at 6, 9, or 12 months of age and from their mothers were assayed for measles antibodies by plaque reduction neutralization. Responses to vaccination with Merck Sharp & Dohme live measles virus vaccines at 9 months (Attenuvax) and 12 months (M-M-R II) were also analyzed., Results: Among women born in the United States (n = 614), geometric mean titers (GMTs) of measles antibodies decreased with increasing birth year. For those born before 1957, 1957 through 1963, and after 1963, GMTs were 4798, 2665, and 989, respectively. Among women born outside of the United States (n = 394), there were no differences in GMTs by year of birth. Children of younger women born in the United States were less likely than those of older women to be seropositive at 6, 9, or 12 months. The response to the vaccines varied by maternal birth year for children of women born in the United States. Among 9-month-old children, 93% of those whose mothers were born after 1963 responded, compared with 77% and 60% of those whose mothers were born in 1957 through 1963 and before 1957, respectively. Among 12-month-old children, 98% of those born to the youngest mothers responded, compared with 90% and 83% of those whose mothers were born in 1957 through 1963 and before 1957. The responses of children of women born outside of the United States were not associated with maternal year of birth., Conclusions: An increasing proportion of children in the United States will respond to the measles vaccine at younger ages because of lower levels of passively acquired maternal measles antibodies.

High morbidity and mortality from measles among infants under 9 months of age is an obstacle to measles control in many developing countries. In this paper, we review 30 studies conducted on the serological response to measles vaccine in infants aged less than 9 months. Among children aged under 9 months, Edmonston Zagreb and AIK-C vaccines produce higher seroresponse rates than Schwarz vaccine of equivalent titre. For Edmonston Zagreb and Schwarz vaccine, seroresponse rates increase with increasing vaccine titre. The absolute rate of seroresponse to Edmonston Zagreb vaccine in 6-month old infants varied greatly between studies because of differences in methods of vaccine titer measurement, serological assays, definitions of seroresponse, and maternal antibody profiles of the populations studied. Seroconversion rates to Edmonston Zagreb or AIK-C vaccines at 6 months of age were generally similar to those to Schwarz vaccine at 9 months of age, but antibody levels were lower after vaccination below 9 months of age. Although the increased mortality documented in other studies after use of high titer vaccines in 4-6 month old infants led to withdrawal of these vaccines, this review of vaccine trials highlights the need for standardization of study methods and for a better understanding of the biological action of measles vaccines.

The Expanded Programme on Immunization (EPI) of the World Health Organization has a global target of reducing measles incidence by 90% and mortality by 95% from pre-EPI levels by 1995. Both developed and developing countries that have given priority to measles control have substantially reduced measles morbidity and mortality, and some have come close to eliminating measles. A variety of vaccination schedules and strategies have been used, which reflect the differing program goals, health services infrastructure, and availability of resources in different countries. Failure to control measles has usually been due to a failure to implement planned strategies adequately. The highest priority in measles control is to assist countries, especially the lowest-income countries, to implement vaccination programs more effectively.

The effect of measles vaccine potency was evaluated among 485 children aged 6 months, and the effect of vaccine strain was evaluated among 538 children aged 3.5 months, in Kinshasa, Zaire. Children aged 6 months were randomly assigned to receive either high-titre Edmonston-Zagreb (EZ-H), potency 5.7 log10/dose, or medium-titre EZ (EZ-M), potency 4.7 log10/dose, those aged 3.5 months were randomly assigned to receive either AIK-C, potency 5.5 log10/dose, or EZ-H, and were revaccinated with EZ-M vaccine at age 9.5 months. Measles antibodies were measured using the plaque reduction neutralization assay. Among children vaccinated at age 6 months, the seroresponse was significantly higher after EZ-H than EZ-M vaccine, with 92 and 83% seroconverting by 6 months postvaccination and 59 and 40% respectively having antibody titres > 200 mIU. Among children vaccinated at age 3.5 months, only 24% (AIK-C) and 22% (EZ-H) attained antibody titres > or = 200 mIU 6 months postvaccination. After revaccination at age 9.5 months, 81% of children in the AIK-C group and 73% in the EZ-H group had antibody levels > 200 mIU (p = 0.056). A retrospective survey was conducted in January 1993 to determine the mortality experience of vaccine groups, and information was obtained for 94% of the children. A total of 44 deaths (4%) were identified, with no significant differences between groups when stratified by age at vaccination.(ABSTRACT TRUNCATED AT 250 WORDS)

Background: To improve measles control in Kinshasa, Zaire, a project to increase vaccine coverage was begun in 1988, and in 1989, the city vaccination programme changed measles vaccination policy from Schwartz vaccine at age 9 months to medium titre Edmonston Zagreb (EZ) vaccine at age 6 months. We report the impact of the programme on measles incidence and mortality., Methods: Data on vaccine coverage were obtained from cluster sample surveys conducted every 1-2 years and from routine reports of vaccine doses administered. Data on measles incidence and mortality were obtained from sentinel surveillance sites. The serological response to EZ measles vaccine was evaluated at a health centre in 1989 and in a community survey in 1990., Results: Measles vaccine coverage estimated in cluster surveys increased from 50% of the 1984 birth cohort to 89% of the 1989 birth cohort, accepting either a home-based record or a verbal history of vaccination. Reported measles incidence per 10,000 [corrected] population decreased by over 90%, from 37.5 in 1980 (early vaccination years) to 1.6 in 1991. There was a relative decrease in the proportion of cases aged < 9 months (32% of cases in 1986-1987 and 23% of cases in 1990-1991) and an increase in the proportion aged > 23 months (29% of cases in 1986-1987 and 43% in 1990-1991). According to ELISA assays, 74-76% of children seroresponded to EZ vaccine administered at age 6-7 months under routine programme conditions., Conclusions: Measles can be controlled in urban areas, although it is difficult to determine how great a contribution vaccination at age 6 months makes over and above the achievement of high coverage.

Prior to measles vaccine use, measles accounted for over 2.5 million deaths annually. Measles epidemiology in the developed countries is different from that in less developed countries. Whereas in the developing world, measles is a disease primarily of young children, particularly infants in urban areas, in the developed world, school-age children > 5 years old play a greater role. Prevention of measles in developing countries has relied principally on a single dose of Schwarz strain vaccine at age 9 months (> 85% efficacy); 80% coverage has prevented > 1.6 million deaths. However, problems have been encountered because of the narrow window to deliver vaccines between the time an infant becomes susceptible and exposure to disease. Recent studies suggest that some strains of measles vaccines given at potencies 10-100 times higher than standard vaccines may achieve good efficacy in infants aged 4-6 months, but safety of these vaccines has been questioned. Widespread use of standard vaccines in the West has resulted in dramatic reductions in measles incidence but has not prevented outbreaks among the 2-5% of persons not protected by a single dose. Such outbreaks often appear after extended periods either without measles or with low measles incidence. A single dose appears adequate to control measles well but inadequate to eliminate the disease. Many developed countries have adopted two-dose schedules. Measles immunization has dramatically reduced measles occurrence, but improved control is necessary to prevent the estimated 1 million deaths still occurring each year.

The use of IgM antibody detection for the classification of the primary and secondary measles antibody response in persons following primary and secondary vaccination and natural measles virus infection was examined. Of 32 nonimmune children receiving primary measles vaccination, 31 (97%) developed IgM antibodies, consistent with a primary antibody response. Of 21 previously vaccinated children with low levels of preexisting IgG antibodies who responded to revaccination, none developed detectable IgM antibodies, whereas 33 of 35 (94%) with no detectable preexisting IgG antibodies developed an IgM response. Of a sample of 57 measles cases with a prior history of vaccination, 55 (96%) had detectable IgM antibodies. Of these, 30 (55%) were classified as having a primary antibody response and 25 (45%) a secondary antibody response based on differences in their ratios of IgM to IgG antibodies. Differences in the severity of clinical symptoms between these 2 groups were consistent with this classification scheme. These findings suggest that 1) an IgM response follows primary measles vaccination in the immunologically naive, 2) an IgM response is absent on revaccination of those previously immunized, and 3) an IgM response may follow clinical measles virus infection independent of prior immunization status.

Measles-mumps-rubella vaccine (MMR) is recommended for human immunodeficiency virus-infected (HIV+) adults. Data concerning MMR vaccination of HIV+ patients are limited to children. We evaluated 39 HIV+ (97% with > 200 CD4+ lymphocytes) and 17 non-HIV+ control adults receiving measles-rubella vaccine (MR). Clinical adverse events did not differ between groups. Prevaccination, three HIV+ and two control vaccinees were measles seronegative; no HIV+ and one control vaccinee seroconverted. No initially measles-seropositive vaccinee had a significant antibody elevation. Four HIV+ and three control vaccinees were rubella seronegative prevaccination; three HIV+ and two control vaccinees seroconverted. Among those initially rubella seropositive, two HIV+ and one control vaccinee had significant antibody elevations. There were no significant percentage CD4+ or CD8+ lymphocyte changes between groups. Three HIV+ vaccinees were p24 antigen positive pre- and postvaccination. Although MR vaccination appears safe in HIV+ adults, questions remain about the response of measles and rubella antibody-negative HIV+ adults and those with < 200 CD4+ lymphocytes.

The response to Edmonston-Zagreb vaccine (titer, 5.4 log10 pfu) was evaluated among children in a study of perinatal transmission of human immunodeficiency virus (HIV) in Kinshasa. Acute postvaccination adverse events were monitored for 49 HIV-infected and 376 non-HIV-infected infants, and measles antibody responses were assessed by ELISA for 34 HIV-infected and 255 non-HIV-infected infants. There was no increase in the incidence of common symptoms 7-10 days after vaccination. HIV-infected infants were more likely to have detectable prevaccination measles antibody, and seroconversion after vaccination was somewhat lower in HIV-infected (76.5%) than non-HIV-infected infants (85.5%). Seroconversion rates did not differ among children with or without rhinitis or fever at vaccination. High-titer Edmonston-Zagreb vaccine given at 6 months of age has the potential to provide earlier protection against measles; however, this vaccine is no longer recommended for routine use, and two doses of standard-titer vaccines remains the preferred option for measles vaccination of HIV-infected infants.

Hungary has had a successful measles vaccination programme, achieving over 93% coverage in targeted groups. However, from September 1988 until December 1989, 17,938 measles cases were reported among the civilian population (attack rate [AR] = 169 per 100,000 population) with the majority of cases occurring in vaccinated people. National surveillance data were analysed to determine reasons for the outbreak and risk factors for vaccine failure. People born during 1971 and 1972 had been targeted for vaccination during campaigns in April and September of 1973 and had the highest AR (1332 and 1632 per 100,000, respectively). Epidemiological studies of vaccine efficacy conducted among secondary school students corroborated these findings. Among 754 secondary school students, those vaccinated during the April 1973 campaign were at highest risk compared with those vaccinated at routine health care after 1974 (relative risk = 10.9, 95% confidence interval [Cl]: 2.5-47.9). Among 341 primary school students, one-dose recipients were at higher risk compared with two-dose recipients controlling for age at and time elapsed since vaccination (P = 0.04).

To evaluate persistence of measles antibody after revaccination, antibody levels were measured 6 years after revaccination of 40 hemagglutination-inhibition (HAI) antibody-negative students who had participated in a serosurvey in Massachusetts. Twelve subjects who had been HAI antibody-positive and were not revaccinated were included as a comparison group. Before revaccination, 7 revaccinees had no detectable plaque reduction neutralization (PRN) antibody (group 1) and 33 had low levels of PRN antibody (group 2). Three weeks after revaccination, all in group 1 and 30 (90%) of 33 in group 2 had developed a fourfold or greater rise in PRN antibody. Six years after revaccination, all subjects had PRN-detectable antibody. However, 12 in group 2 (36%) had antibody titers less than or equal to 1:120 compared with none in group 1 (P less than .01). Persons without PRN antibody will respond to revaccination and maintain protective antibody titers. In contrast, persons with low levels of PRN antibody may respond initially to revaccination, but their antibody titers may fall again to low levels.

A record audit of 254 children attending a public clinic in Los Angeles was conducted to assess immunization levels prior to a measles outbreak in the community. Coverage with all vaccines appropriate for age decreased from 67% at 3 months to 25% at 19 months. Delay in initiating vaccination was associated with increasing risk for delayed measles-mumps-rubella vaccine beyond age 2 years (P less than .05). In one third of children, health care providers missed an opportunity to administer measles-mumps-rubella vaccine. Recall systems and elimination of missed opportunities may increase vaccination levels in clinic populations. Record audits should be considered for use in guiding the management of immunization programs.

Between February 8 and April 4, 1986, an outbreak of measles occurred in the State of Arkansas. A total of 489 suspected measles cases were reported from 53 counties; 86 schools statewide reported suspected measles cases. There were 284 cases confirmed in 18 counties; 23.6 percent among students in one university and 41.2 percent among students in kindergarten through 12th grade in 32 schools. An epidemiologic investigation was carried out to evaluate risk factors for vaccine failure and to assess the effectiveness of a selective revaccination strategy in the outbreak setting. A cohort study conducted at a junior high school showed that, compared with students vaccinated against measles at ages 15 months or older, those vaccinated at ages 12-14 months had a three-fold increased risk of measles (relative risk 3.2, 95 percent confidence interval 1.5, 6.9). For schools reporting measles, the Arkansas Department of Health and the Department of Education jointly required reimmunization of students vaccinated at ages younger than 15 months and the exclusion of students not vaccinated at ages 15 months or older until they were vaccinated or until 2 weeks after the last rash onset. To implement these recommendations, more than 100,000 doses of combined measles-mumps-rubella vaccine were distributed at a cost greater than $1 million.

Because of increased measles incidence in the United States during 1989 and 1990 and the recent finding of genomic differences between vaccine virus and contemporary wild measles viruses, we conducted a study to determine whether the current measles vaccine had become less effective. Household secondary attack rates for 203 California children ages 1 to 5 years were 4.2 and 77.8% for vaccinated and unvaccinated children, respectively, and the vaccine efficacy was 95% (95% confidence interval: 89%, 97%). The protective efficacy for postexposure vaccination and use of IG were both low, 4% (95% confidence interval: less than 0, 36%) and 8% (95% confidence interval: less than 0, 59%), respectively. The measles vaccine efficacy found in this study is similar to those obtained in previous years and indicates that the measles epidemic of 1989 to 1990 occurred despite high vaccine effectiveness.

We studied adverse events reported by 401 measles, mumps and rubella (MMR) vaccinees and 391 unvaccinated controls at one college, and 133 measles (M) vaccinees and 352 unvaccinated controls at an adjacent college during a measles outbreak in Massachusetts in 1985. Rates of symptoms and signs experienced by MMR vaccinees, M vaccinees, and controls were essentially similar. No serious adverse events were detected.

Measles is a major cause of acute lower respiratory infection (ALRI) in developing countries. Hospital and community-based studies of ALRI have found that measles accounts for 6%-21% of the morbidity and 8%-93% of the mortality due to ALRI. Although live attenuated measles vaccine is one of the most effective vaccines in use today, measles has not been controlled in many parts of the world, primarily because the levels of vaccine coverage required to interrupt measles transmission have not been achieved. In addition, in some areas, a large percentage of cases of measles occur in infants who are younger than the age recommended for vaccination. Recent studies suggest that the Edmonston-Zagreb measles vaccine may be more immunogenic than other vaccine strains in young infants. A substantial proportion of ALRI could be prevented by increasing measles vaccine coverage and by the use of particular vaccine strains in younger children.

Background: In early 1988 an outbreak of 84 measles cases occurred at a college in Colorado in which over 98 percent of students had documentation of adequate measles immunity (physician diagnosed measles, receipt of live measles vaccine on or after the first birthday, or serologic evidence of immunity) due to an immunization requirement in effect since 1986., Methods: To examine potential risk factors for measles vaccine failure, we conducted a retrospective cohort study among students living in campus dormitories using student health service vaccination records., Results: Overall, 70 (83 percent) cases had been vaccinated at greater than or equal to 12 months of age. Students living in campus dormitories were at increased risk for measles compared to students living off-campus (RR = 3.0, 95% CI = 2.0, 4.7). Students vaccinated at 12-14 months of age were at increased risk compared to those vaccinated at greater than or equal to 15 months (RR = 3.1, 95% CI = 1.7, 5.7). Time since vaccination was not a risk factor for vaccine failure. Measles vaccine effectiveness was calculated to be 94% (95% CI = 86, 98) for vaccination at greater than or equal to 15 months., Conclusions: As in secondary schools, measles outbreaks can occur among highly vaccinated college populations. Implementation of recent recommendations to require two doses of measles vaccine for college entrants should help reduce measles outbreaks in college populations.

Persons who received measles vaccine between 12 and 14 months of age have been found to be at increased risk of measles compared with those vaccinated at greater than or equal to 15 months of age. Because of this, in 1987 the Immunization Practices Advisory Committee of the US Public Health Service recommended that, during measles outbreaks, revaccination of persons vaccinated at 12-14 months of age be considered. During a school-based outbreak in New Mexico in 1987, the authors evaluated the effect of a mandatory revaccination policy in affected schools. Before the effect of revaccination, the overall attack rate in persons vaccinated at greater than or equal to 12 months of age was 4.1 cases/1,000 students; afterward, the risk was significantly reduced by 73%, to 1.1/1,000 students. The attack rate among students targeted for revaccination declined 100%, compared with 41% among those not revaccinated. Overall, attack rates were significantly lower in schools conducting revaccination early compared with schools holding later revaccination. In a retrospective cohort study of single-dose vaccines in one school, age at vaccination was not associated with risk of disease; however, persons vaccinated greater than or equal to 10 years before the outbreak were at increased risk, independently of age at vaccination. Revaccination of persons whose most recent vaccination was between 12 and 14 months of age appeared to control transmission in this outbreak. Further studies are needed to confirm these observations and to evaluate the effect of other revaccination efforts during outbreaks.

Measles vaccine is one of the safest and most effective vaccines currently available. Use of the vaccine has decreased the incidence of measles in both developed and developing countries. Nevertheless, preventable morbidity and mortality continue to occur. In the United States, the measles problem differs when it occurs among preschool-aged children or school-aged children. The former is a due to insufficient vaccine delivery. For measles in school-aged and college students, the problem is primarily vaccine failure, which should eventually be solved by a two-dose schedule. In developing countries, the major problem is vaccine delivery. Use of Edmonston-Zagreb measles vaccine in developing countries offers the promise of reducing disease rates in young infants; however, in both the United States and in developing countries, increasing immunization levels is essential.

Because measles causes an estimated 2 million deaths per year among children in developing countries, including a substantial proportion of infants less than nine months old--the age at which vaccination is recommended--there has been interest in using different strains of vaccine and higher doses to achieve immunization of younger infants. We conducted a randomized trial of three different doses of Edmonston-Zagreb and of Schwarz measles vaccines in infants to evaluate the effect of the strain and dose of vaccine on the serologic response and acute adverse reactions to vaccination. Six-month-old infants received a standard, medium, or high dose of one of the vaccines, and nine-month-old infants received a standard dose. Antibody levels were measured before and after vaccination, by means of a plaque-reduction neutralization assay, in 1061 six-month-olds and 299 nine-month-olds. Edmonston-Zagreb vaccine produced higher rates of seroconversion and seropositivity than comparable doses of Schwarz vaccine. Among the six-month-old infants, the seroconversion rate 18 weeks after vaccination with the standard dose of Edmonston-Zagreb vaccine was 92 percent, that with the medium dose was 96 to 97 percent, and that with the high dose was 98 percent; the rates for the corresponding doses of Schwarz vaccine were 66 percent, 76 percent, and 91 percent, respectively. Higher seroconversion rates were observed with an increase in the dose of either Edmonston-Zagreb (P less than 0.01) or Schwarz (P less than 0.001) vaccine. The seroconversion rates produced by high and medium doses of Edmonston-Zagreb vaccine in six-month-olds were equal to or significantly higher than the rate produced by a standard dose of Schwarz vaccine in nine-month-olds (87 percent). Clinical adverse reactions were not associated with the strain or dose of a vaccine. We conclude that Edmonston-Zagreb vaccine is more immunogenic than Schwarz vaccine in infants and can induce effective immunization against measles at six months of age.

A measles outbreak in an inner-city area primarily involved preschool-aged children younger than 5 years of age. The reasons why 31 unvaccinated preschool children with measles disease had not been vaccinated were investigated. For some patients, health care providers missed opportunities to vaccinate eligible patients against measles. Of the 26 patients whose full immunization status was known, ten (38%) were vaccinated with diphtheria and tetanus toxoids and pertussis vaccine and/or oral poliovirus vaccine at a time when they could have received measles vaccine simultaneously, according to recommendations of the Immunization Practices Advisory Committee and the American Academy of Pediatrics. In addition, five of ten health care providers interviewed missed at least one opportunity to administer measles vaccine because of a minor illness that was not a contraindication to vaccination. Unvaccinated patients were more likely to receive health care in the public sector, have single mothers, and have parents who had no knowledge of existing vaccines; they were less likely to be age-appropriately immunized with other antigens. If measles immunization levels among preschool children in the United States are to be increased, education of both health care providers and parents, coupled with innovative strategies targeted to preschool children, particularly of low socioeconomic groups in inner cities, are needed.

Recently studies conducted in several countries using Edmonston-Zagreb vaccine administered subcutaneously to infants younger than 9 months of age have shown high seroconversion rates, approaching or equaling those routinely achieved at 9 months of age with the more widely used Schwarz vaccine. These results have raised expectations that the Edmonston-Zagreb vaccine can play an important role in helping to prevent measles in young infants in highly endemic areas. Because of the implications of changing the measles vaccine recommendations, vaccine advisory groups and vaccine manufacturers will require additional studies to confirm the preliminary findings and to answer new questions which have been raised. The needed data will probably be collected over the next year or two in studies already under way or being planned in the hope that a more effective vaccine for young infants can be introduced before the end of this decade.