Measles control in the United States: problems of the past and challenges for the future

Elimination of indigenous measles from the United States has been a public priority since 1978. To assess the progress made toward this goal, we review the epidemiology of measles from 1963 to the present. From the 1970s through early into the recent measles epidemic, the majority of measles cases were in highly vaccinated, school-age children. This was due primarily to a 1 to 5% primary measles-mumps-rubella vaccine failure rate and nonrandom mixing patterns among school-age populations. To eliminate susceptible individuals in the school-age populations, a second dose of measles vaccine is now recommended between 5 and 6 years or 11 and 12 years by both the Advisory Committee on Immunization Practices and the American Academy of Pediatrics. Later in the epidemic, measles cases surged among unimmunized preschool children, especially among the poor in inner-city areas. Immunization rates have been documented to be low among preschool populations because of missed opportunities to administer vaccines at all health visits and barriers to access to immunizations. To raise immunization rates, the age for the first measles-mumps-rubella immunization was lowered to 12 to 15 months of age, federal immunization funding has increased, and new standards for immunization delivery have been developed and promulgated.

[Immunity to measles, mumps and rubella in children vaccinated with triple viral vaccine]

OBJECTIVE

To check up on measles-mumps-rubella immunity in children vaccinated with MMR vaccine.

DESIGN

A descriptive cross-sectional study trough seroepidemiological survey.

SETTING

Oliver-Miralbueno Health Centre, Zaragoza.

PATIENTS

92 healthy children of 5, 7 and 9 years of age who went for clinical preventive services. All of them vaccinated with MMR at the age of 15 to 18 months. None of them had suffered from measles, mumps or rubella.

MEASUREMENTS AND MAIN RESULTS

1) The percentage of seronegative children (title less than 1:8) was: 9.8% for measles, 8.7% for rubella, and 27.2% for mumps. 2) As to the time differences among seropositive and seronegative children.

CONCLUSIONS

The study reveals that there is a high percentage of MMR vaccinated children showing minimal or undetectable levels of antibodies.

[Arguments against routine mumps vaccination]

Routine immunization against mumps was included in the MMR-elimination-programme of Switzerland despite the lack of any public health necessity. Seven years later, the theoretical presumptions of the mumps immunization campaign are challenged by practical experiences: An unnecessary vaccination proves to be of insufficient efficacy, yet associated with an unexpected high complication rate and bears thus the risk of discrediting also other immunizations in the general public. What could be considered a particular immunization failure reveals important inconsistencies of the entire MMR-mass-immunization-campaign. The project remains epidemiologically highly vulnerable and thus hazardous. Because of its constraining effects on the general population, compatibility with basic civil rights can be questioned. The reasons why some 20% of the Swiss population refuse mumps vaccination are little investigated so far. Nevertheless, research can provide important clues for further investigations in this field. As the maturation of the immune system follows learning principles, the question arises whether childhood diseases are not essential for the normal development of immunocompetence. In cancer therapy new attention is drawn to hyperthermia and thus to the healing potential of fever. And finally, there are concerns about the longterm effects of manipulations of the natural balance between man and microorganisms.

[Does a modified vaccination schedule protect better against measles?]

OBJECTIVE

To assess the value of an alternative vaccination programme (VP) with Mumps-Measles-Rubella (MMR) vaccine at the ages of 12 and 15 months compared with the standard VP (MMR at the ages of 14-15 months and 9 years).

DESIGN

Cross-sectional study.

SETTING

The area of activity of the 'Lek and Merwede' Extramural Health Care Department.

METHOD

Data from general practitioners (GPs) and from an inquiry among parents of 873 children born in a 1.5 year period (randomly taken among 4500 children) and given the alternative MMR VP, were used. The inquiry took place during a measles epidemic in 1993. A non-response study was also executed among the parents.

RESULTS

The response of the GPs was low (14 cases reported by 8 out of 90 GPs). Eighty-two per cent of the parents responded. There was no correlation between (non-)response and the alternative VP. The vaccination was effective and no significant differences between standard and alternative VP were found.

CONCLUSION

Vaccination protects against measles. An alternative VP could theoretically be more effective, but because of the excellent results of the standard VP differences could not be detected.

The elimination of indigenous measles, mumps, and rubella from Finland by a 12-year, two-dose vaccination program

BACKGROUND

In the 1970s measles, mumps, and rubella were rampant in Finland, and rates of immunization were inadequate. In 1982 a comprehensive national vaccination program began in which two doses of a combined live-virus vaccine were used.

METHODS

Public health nurses at 1036 child health centers administered the vaccine to children at 14 to 18 months of age and again at 6 years, and also to selected groups of older children and young adults. Vaccination was voluntary and free of charge. In follow-up studies, we focused on rates of vaccination, reasons for noncompliance, adverse reactions, immunogenicity, persistence of antibody, and incidence of the three diseases. Since 1987, paired serum samples have been collected from all patients with suspected cases of measles, mumps, or rubella.

RESULTS

Over a period of 12 years, 1.5 million of the 5 million people in Finland were vaccinated. Coverage now exceeds 95 percent. The vaccine was efficient and safe, even in those with a history of severe allergy. No deaths or persistent sequelae were attributable to vaccination. The most frequent complication requiring hospitalization was acute thrombocytopenic purpura, which occurred at a rate of 3.3 per 100,000 vaccinated persons. The 99 percent decrease in the incidence of the three diseases was accompanied by an increasing rate of false positive clinical diagnoses. In 655 vaccinated patients with clinically diagnosed disease, serologic studies confirmed the presence of measles in only 0.8 percent, mumps in 2.0 percent, and rubella in 1.2 percent. The few localized outbreaks were confined to patients in the partially vaccinated age groups. There are now fewer than 30 sporadic cases of each of the three diseases per year, and those are probably imported.

CONCLUSIONS

Over a 12-year period, an immunization program using two doses of combined live-virus vaccine has eliminated indigenous measles, mumps, and rubella from Finland. Serologic studies show that most reported sporadic cases are now due to other causes, but a continued high rate of vaccination coverage is essential to prevent outbreaks resulting from exposure to imported disease.

Risk factors for delayed immunization among children in an HMO

OBJECTIVES

Improving the timely delivery of childhood immunizations has become a national imperative. This study aimed to identify nonfinancial predictors of delayed immunization among patients with good financial access to preventive care.

METHODS

This prospective cohort study used telephone interviews and a computerized immunization tracking system to evaluate 13-month-old children (n = 530) in a regional group-model health maintenance organization.

RESULTS

More than one third of parents interviewed did not know when the next immunization was due. Thirteen percent were late for the measles-mumps-rubella immunization, recommended at 15 months of age, by 90 days or more. Independent predictors of delayed immunization included having a larger number of children (odds ratio [OR] = 1.4, P < .01), not having a regular doctor (OR = 2.9, P < .05), not knowing when the shot was due (OR = 2.0, P < .01), and not worrying about the risks of shots (OR = 1.4, P < .05).

CONCLUSIONS

Financial access alone does not guarantee timely childhood immunization. In managed care settings, which may cover increasing numbers of children under health care reform, interventions are needed to better inform parents of when immunizations are due.

Intent to immunize among pediatric and family medicine residents

OBJECTIVE

To determine whether contraindications to immunization are inappropriately broadened for children with a fever or a neurologic condition.

PARTICIPANTS

Pediatric and family medicine residents (N = 52 and 23, respectively) at the University of Rochester (NY).

DESIGN

Cross-sectional survey. Residents rated how likely they would be to administer a diphtheria-tetanus-pertussis or measles-mumps-rubella vaccine in 17 clinical scenarios according to a rating scale ranging from 1 (never) to 5 (always). For all scenarios, the immunization was recommended by the American Academy of Pediatrics or the Immunization Practices Advisory Committee.

RESULTS

In only five and three of 17 scenarios would 90% or more of the pediatric residents and family medicine residents, respectively, have administered an immunization. For diphtheria-tetanus-pertussis vaccine, pediatric residents reported a lower likelihood of vaccinating a 2-month-old child with a low fever (temperature, 38.1 degrees C) than an afebrile child (mean score, 3.0 vs 4.7; P < .01). A 2-year-old child with idiopathic epilepsy, a 2-month-old child with intraventricular hemorrhage, and a 2-month-old child who had a parent with a seizure disorder each had a lower reported likelihood to be vaccinated than a same-aged child without a neurologic condition (2.8 vs 4.5; 4.1 vs 4.7; and 4.3 vs 4.7, respectively; each P < .01). For measles-mumps-rubella, pediatric residents reported a lower likelihood of vaccinating a 15-month-old child with a low fever than an afebrile child (4.2 vs 4.9; P < .01). A child with a progressive neurologic disease had a lower reported likelihood to be vaccinated than a child without a neurologic condition (3.5 vs 4.9; P < .01).

CONCLUSIONS

Residents reported a lower likelihood of immunizing children with a fever or neurologic condition. Such practice styles may contribute to underimmunization. Residents need to be educated regarding which medical conditions contraindicate an immunization.

Potential impact on vaccination coverage levels by administering vaccines simultaneously and reducing dropout rates

BACKGROUND

Retrospective immunization coverage surveys conducted during 1991 and 1992 demonstrated that coverage levels for the routine childhood vaccines by 24 months of age in selected urban areas of the United States ranged from 10% to 52%, far below the US Public Health Service goal of 90%. Therefore, appropriate programmatic changes must be identified and incorporated.

METHODS

We analyzed coverage survey data collected from 21 sites to measure the potential impact on coverage levels of implementing selected changes in vaccination practices. In a multistaged cluster survey design, school health records of kindergarten or first-grade students were randomly selected and dates of vaccination assessed. We evaluated changes in the vaccination practices, such as eliminating missed opportunities for simultaneous administration of vaccines and ensuring that children initiated the vaccination series on time (ie, by 3 months of age). We then calculated potential increases in coverage levels for a best-case scenario.

RESULTS

From 77% to 96% of all children in the 21 sites had received at least one vaccination by their first birthday. Children were 2.3 to 17 times more likely to be up to date on their vaccinations by 24 months of age if they were up to date at 3 months of age. Each child had many opportunities for the simultaneous administration of diphtheria and tetanus toxoids and pertussis (DTP) vaccine, oral polio vaccine (OPV), and measles-mumps-rubella (MMR) vaccine that, if used appropriately, could have potentially raised coverage levels by 12% to 22% (median, 17%). The highest coverage levels could have been attained if all children had started the series on time and if advantage had been taken of all opportunities for simultaneous vaccination. Coverage levels for four doses of DTP vaccine, three doses of OPV, and one dose of MMR vaccine would have increased from a baseline of 10% to 52% to levels of 54% to 83%.

CONCLUSIONS

Although the majority of children received a vaccination by their first birthday, the coverage level at 24 months of age was low. Tracking systems are needed to ensure that children do not drop out of the system once they have begun the vaccination series. In addition, all children who are late in beginning their vaccination series are at increased risk of not completing the recommended vaccination series on time, and these children need intensive follow-up and recall efforts. Also, providers need to administer all needed vaccines simultaneously.

[Mumps--occupational exposure and aspects of epidemiologic susceptibility]

1041 persons working in the university hospital of Freiburg, Germany, were tested for mumps antibodies. The first part of the investigation was conducted between 1986 and 1988, the second one in 1992. Significant decrease in seroprevalence between study I (67% immune) and study II (63% immune) was found. Average immunity of paediatric nurses was significantly higher (76%) than that of non-exposed persons (59.7%). 195 persons were vaccinated (live vaccine) and 84.6% seroconverted.

Responses to measles immunization in children infected with human immunodeficiency virus

The responses to measles immunization administered between 6 and 12 months and after 12 months were compared in children with and without human immunodeficiency virus infection. No difference in response was found when primary measles immunization was administered between 6 and 12 months; however, children with human immunodeficiency virus infection had a significantly poorer response when immunization was given after 12 months. Early measles immunization should be considered in children with human immunodeficiency virus infection.

Measles immunization of 2-year-olds in a rural southern state

OBJECTIVE

To assess the measles vaccine coverage of 2-year-old children living in Mississippi during the national measles epidemic of 1989 and 1990.

DESIGN

Survey of 2-year-olds randomly selected from the 1987 birth cohort. The status of measles-mumps-rubella (MMR) vaccination was determined by medical record reviews and family contacts.

SETTING

A predominantly rural state in the southeastern United States with a large black minority population (35%) and a low per capital income ($9827 to $12,899). Approximately 80% of MMR immunizations are given by public health service nurses working in nine health districts.

SUBJECTS

A total of 2450 preschool-aged children representing 6% of the 1987 birth cohort (n = 41,279). Three hundred forty-one children were considered ineligible, leaving 2109 in the final sample.

MAIN OUTCOME MEASURES

Confirmed vaccination by the age of 2 years. Rates of immunization were calculated for the entire state, its health districts, and subgroups based on population density, per capita income, type of clinic visited, and race.

RESULTS

The statewide immunization rate was 87% (95% confidence interval, 86% to 88%). Among the nine health districts, rates varied from 79% to 97% (median, 88%). They were similar for white and black children in each health district and within the state as a whole. The level of vaccine coverage was significantly higher in districts with lower population densities (89% vs 85%, P = .02) and in those with higher per capita incomes (89% vs 86%, P = .03). There were four minor outbreaks of measles during 1989 and 1990; half of the cases occurred in unimmunized children too young to receive the MMR vaccine.

CONCLUSION

A high rate of measles immunization is attainable among 2-year-olds living in a rural state with a large black minority population and limited economic resources.

Vaccination coverage of 2-year-old children--United States, 1992-1993

The principal goal of the Childhood Immunization Initiative (CII) is to increase, by 1996, vaccination levels for 2-year-old children to at least 90% for the most critical doses in the vaccination series (i.e., one dose of measles-mumps-rubella vaccine [MMR] and at least three doses each of diphtheria and tetanus toxoids and pertussis vaccine [DTP], oral poliovirus vaccine [OPV], and Haemophilus influenzae type b vaccine [Hib]) and to at least 70% for at least three doses of hepatitis B vaccine (Hep B). Since 1991, annual national estimates of vaccination coverage levels of preschool-aged children have been available through the National Health Interview Survey (NHIS) conducted by CDC. This report presents vaccination coverage levels of children aged 19-35 months for 1992 and provisional estimates of vaccination coverage for the combined first and second quarters of 1993 (Table 1).