Public health surveillance for smallpox - United States, 2003-2005.

In June 1987, nearly 10 years after the World Health Organization (WHO) declared smallpox eradicated, the Council of State and Territorial Epidemiologists (CSTE) recommended removal of smallpox, a highly contagious viral disease, from the National Notifiable Diseases Surveillance System (NNDSS). However, the attacks of September 11, 2001, raised concern that smallpox (variola) virus, might exist in laboratories other than two WHO-designated repositories and could be used as an agent of biologic terrorism. In response to this concern, CSTE and CDC recommended in June 2003 that smallpox again be made reportable through NNDSS and that all states, territories, and cities add smallpox to their lists of reportable diseases. In 2005, CSTE conducted a cross-sectional survey in the United States and its territories to assess key components for surveillance of suspected smallpox disease, including legal reporting requirements, laboratory testing, and training and education (e.g., oral presentations and guides). This report summarizes the results of that survey, which indicated that 100% had the capacity to receive and investigate reports, 94% of states had legal requirements to report suspected smallpox disease, 70% had mandatory laboratory reporting of results indicative of smallpox disease, and 68% were providing ongoing training and education of health-care providers and public health staff.

Evaluation of an early two-dose measles vaccination schedule.

Vaccination at 6 months of age followed by routine revaccination is recommended when exposure of infants to measles is likely. Dade County, Florida, began this early two-dose schedule during a large epidemic in 1986-1987 (i.e., 22% of cases occurred in infants aged 6-11 months). This schedule was continued routinely in high-risk areas. The effect of an early two-dose schedule on measles prevention in the county was examined by comparing measles vaccination coverage and epidemiology before (1985-1987) and after (1988-1996) the schedule became routine. To assess serologic response, seroprevalence of measles antibody among children aged 4-6 years in 1995 was examined. To evaluate vaccine effectiveness, a case-control study was conducted among preschool-aged children. Among those aged 2 years, vaccination coverage with > or =1 dose increased from 75% to 94% in 1996. The number of annual cases declined, and endemic measles transmission reportedly ended after 1993. Seroprevalence of plaque reduction neutralization antibody (titer > 1:120) among those receiving vaccination according to an early two-dose schedule and a single dose at age > or =12 months was 94% (95% confidence interval: 89, 98) and 98% (95% confidence interval: 95, 100). In these groups, vaccine effectiveness was comparably high. Early two-dose measles vaccination is associated with improved coverage and a comparably high level of humoral immunity and clinical protection as a single dose at age > or =12 months. This strategy can be useful in areas at high risk for measles among infants.

National serologic survey of measles immunity among persons 6 years of age or older, 1988-1994.

CONTEXT: Measles incidence in the United States is at a record low, and indigenous transmission has been interrupted in each year since 1996, suggesting that measles is no longer endemic. A national estimate of measles immunity and an understanding of predictors of measles susceptibility are essential for assuring sustained elimination of endemic disease. OBJECTIVE: To assess patterns of immunity and to determine predictors of susceptibility to measles. DESIGN/SETTING: Sera and data on participants from the third National Health and Nutrition Examination Survey (1988-1994) (NHANES III) were examined. NHANES III was a cross-sectional survey of a representative sample of the civilian, noninstitutionalized population of the United States. POPULATION: 20,100 persons 6 years of age or older were tested for measles-specific immunoglobulin G (IgG) antibody by an enzyme immunoassay. MAIN OUTCOME MEASURE: Participants with serum positive for measles antibody were considered protected or immune to measles disease. RESULTS: Prevalence of measles immunity was 93%. Nearly all persons (99%) born in the prevaccine era (before 1957) were immune. Immunity declined among persons born in the vaccine era (after 1956) to 81% among those born in 1967-1976, and increased again to 89% among those born in 1977-1988. Among persons born in the vaccine era, independent predictors of measles susceptibility varied by birth cohort and included birth in the United States, residence in a noncrowded household, residence in a nonmetropolitan area, and, among males, non-Hispanic white and Mexican American race/ethnicity. Among adults 17 years of age or older, additional predictors of susceptibility included living at or above the poverty line and not currently being married. CONCLUSIONS: Population immunity among persons 6 years of age or older is very high; however, as many as 15 million persons across the United States may lack humoral immunity. While it is unclear that the susceptible population can support continuous, indigenous transmission of measles, providers should follow current recommendations to evaluate the measles susceptibility of patients born in the vaccine era and vaccinate eligible patients.

Assessing immunization coverage in private practice.

To achieve national health objectives of eliminating most childhood vaccine-preventable diseases by the year 2010, all health care providers will have to improve the immunization rates of their patients. Currently, immunization rates of children 19 to 35 months of age are less than national objectives, suggesting a need for optimized immunization services. A key strategy for improving age-appropriate immunization coverage by health care providers is the assessment of immunization coverage. Because most (62%), immunization services in the United States are delivered in the private sector, a concerted effort in private practice is critical to improving immunization rates. Assessment of immunization coverage of patients enrolled in private practice serves 1) to measure the overall performance of the practice in providing the standard of care, 2) to identify strategies for improving coverage, and 3) to document the quality of health services delivered (report card). Assessment of immunization coverage has been demonstrated in several practice settings to be highly effective in improving immunization rates. All types of physicians should benefit from assessing immunization coverage of their patients. Simple assessment tools are available at no cost to the public and can be obtained by contacting the Centers for Disease Control and Prevention. These tools include a manual self-assessment or a computerized software package (CASA) to fit the needs of the practice.

Effectiveness and cost-effectiveness of linking the special supplemental program for women, infants, and children (WIC) and immunization activities.

OBJECTIVE: To raise immunization coverage among children at risk for underimmunization, we evaluated the effectiveness and cost-effectiveness of immunization activities in the Special Supplemental Program for Women, Infants and Children (WIC). METHOD: A controlled intervention trial was conducted in seven WIC sites in Chicago between October 1990 and March 1994. At intervention sites, staff screened children for vaccination status at every visit, referred vaccine-eligible children to either an on-site WIC nurse, on-site clinic, or off-site community provider, and issued either a 3-month supply of food vouchers to up-to-date children or a 1-month supply to children not up-to-date--a usual practice for high-risk WIC children. Our primary measure of effectiveness was the change in the baseline percentage of up-to-date children at the second birthday; cost-effectiveness was approximated for each of the three referral interventions. RESULTS: After one year, up-to-date vaccination coverage increased 23% above baseline for intervention groups and decreased 9% in the control group. After the second year, up-to-date vaccination further increased to 38% above baseline in intervention groups and did not change in the control group. The total cost per additional up-to-date child ranged from $30 for sites referring children off-site to $73 for sites referring children on-site to a nurse. CONCLUSION: This controlled intervention trial of screening, referral, and a voucher incentive in the WIC program demonstrated a substantial increase in immunization coverage at a low cost. Continuing to design linkages between WIC and immunization programs by building on WIC's access to at-risk populations is worth the investment.

Immunization coverage among infants enrolled in the Tennessee Medicaid program.

OBJECTIVES: To determine immunization coverage of infants receiving Medicaid in Tennessee and to identify risk factors for failure to complete recommended vaccinations by 24 months of age. DESIGN: Retrospective cohort study. SUBJECTS: A total of 33,615 children born in one of three urban Tennessee counties from 1980 through 1989 who were enrolled in Medicaid throughout their first 24 months of life. MAIN OUTCOME MEASURES: Receipt of four diphtheria-tetanus-pertussis, three oral polio, and one measles-mumps-rubella vaccines by 24 months of age (up-to-date), as recorded in computerized county immunization records and Medicaid billing files. RESULTS: Overall, 45% of infants enrolled in Medicaid in the three urban counties completed the recommended vaccinations by 24 months. The proportion of infants up-to-date peaked at 50% for those born in 1982 and 1983, and decreased to 44% for those born in 1989. The only strong independent predictors of immunization completion were number of prior births for the mother, timing of the first immunization, and county of birth. The proportion up-to-date was 56% for first-born children compared with 27% for those whose mothers had at least three prior births; 55% for those whose first immunization was on time compared with 22% for those with a delay in the first immunization; and 63%, 52%, and 37% for infants born in the three respective counties. Maternal age, education, race, and marital status predicted immunization completeness only weakly or not at all. CONCLUSIONS: Of infants born in the three counties in the 1980s who were enrolled in the Tennessee Medicaid program, fewer than half completed their recommended childhood vaccinations by 24 months of age. The large differences in immunization levels between infants enrolled in the Medicaid program in the three counties, not accounted for by differences in demographics, suggest that factors related to the health care and vaccine delivery system have important effects on achieving adequate immunization of these infants.

Preschool children at high risk for measles: opportunities to vaccinate.

OBJECTIVES: In 1989 and 1990 the United States experienced a measles epidemic with more than 18,000 and 27,000 reported cases, respectively. Nearly half of all persons with measles were unvaccinated preschool children under 5 years of age. We sought to identify potential sites for vaccine delivery. METHODS: Preschool children with measles were surveyed in five inner cities with measles outbreaks in 1989 to 1990 to assess the children's use of health care services and federal assistance programs before contracting measles. RESULTS: Of 972 case children surveyed, 618 (64%) were eligible for measles vaccination at measles onset. Of those, 93% had previously visited a health care provider (private physician, public clinic, hospital emergency department, or hospital outpatient department) and 65% were enrolled in a federal assistance program (AFDC, WIC, or food stamps). Based on parent-reported reasons for health care visits, in Dallas and New York City, health care providers of 24% of 172 children may have missed at least one opportunity to administer measles vaccine. CONCLUSIONS: Many potential opportunities exist to raise the vaccination coverage of unvaccinated preschool children. These opportunities depend on (1) health care providers taking advantage of all opportunities to vaccinate, and (2) immunization services being linked to federal assistance programs.

Studies of missed opportunities for immunization in developing and industrialized countries.

Missed opportunities for immunization are an obstacle to raising immunization coverage among children and women of childbearing age. To determine their global magnitude and reasons, studies reported up to July 1991 were reviewed. A standard measure for the prevalence of missed opportunities was calculated for each study. Seventy-nine studies were identified from 45 countries; 18 were population-based, 52 were health-service-based, and 9 were intervention trials. A median of 32% (range, 0-99%) of the children and women of childbearing age who were surveyed had missed opportunities during visits to the health services for immunization or other reasons. Missed opportunities were mainly due to failure to administer simultaneously all vaccines for which a child was eligible; false contraindications; health workers' practices, including not opening a multidose vaccine vial for a small number of persons to avoid vaccine wastage; and logistical problems. To eliminate missed opportunities for immunization, programmes should emphasize routine supervision and periodic in-service training of health workers which would ensure simultaneous immunizations, reinforce information about true contraindications, and improve health workers' practices.

PIP: The authors review studies reported up to July, 1991, on the global magnitude of and reasons for missed opportunities to immunize children and women of childbearing age. A standard measure was calculated for the prevalence of missed opportunities for each of the 79 studies identified from 45 countries; 18 were population-based, 52 were health-service-based, and 9 were intervention trials. A median of 32% over a range of 0-99% children and women of childbearing age surveyed had missed opportunities during visits to health services for immunization or other reasons. These outcomes were due mainly to the future to administer simultaneously all vaccines for which a child was eligible; false contraindications; health workers' practices; and logistical problems. To eliminate these missed opportunities, programs should emphasize routine supervision and the periodic in-service training of health workers. This approach would ensure simultaneous immunizations, reinforce information about true contraindications, and improve health workers' practices.

Epidemiology of measles in the United States in 1989 and 1990.

During 1989 and 1990 measles incidence increased sharply in the United States. We compared cases reported during these years with those reported between 1981 and 1988. Incidence increased 462% in 1989, and incidence in 1990 (11.2/100,000) was the highest in more than a decade. Although all ages were affected the greatest increases were in children < 5 years and in adults. Incidence was 7- to 10-fold higher among racial/ethnic minority preschoolers than whites, and 80% of vaccine-eligible preschool age cases were unvaccinated. Complications occurred in 9418 (20.5%) cases, most frequently in young children and adults. Large urban outbreaks affecting predominantly unvaccinated preschoolers were common; 47% of all cases reported in 1990 were associated with 5 outbreaks. Reasons for the increased incidence are not clear. Current information suggests no change in vaccination coverage among preschool age children or in vaccine efficacy. Continued surveillance and evaluation of epidemiologic and laboratory data are necessary. The most pressing need is to improve age-appropriate vaccination among preschool age children.

A school-based measles outbreak: the effect of a selective revaccination policy and risk factors for vaccine failure.

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 outbreak among unvaccinated preschool-aged children: opportunities missed by health care providers to administer measles vaccine.

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.

Current epidemiology of pertussis in the United States.

The incidence of pertussis in the United States decreased rapidly during the 20th century, with the most impressive decreases resulting from the widespread use of DTP vaccine since the late 1940's. As a result of immunization laws, vaccine coverage levels against pertussis at school entry have been greater than 95% since 1980. National surveillance for pertussis done by the Centers for Disease Control (CDC) consists of two parts: a weekly telephone reporting system and a written case report system providing more detailed demographic, clinical, and laboratory information. In addition, data on secondary spread of pertussis among household contacts of reported cases were available on a small proportion of reported cases during 1979-1983. During the period 1980-1986, a total of 17,396 cases of pertussis was reported to CDC by weekly telephone reports. The annual incidence of reported pertussis rose during this period from 0.5 cases per 100,000 population to 1.7/100,000. Infants less than 12 months of age had the highest average annual incidence, estimated at 32 cases per 100,000. Children 1-4 years of age accounted for 25% of all cases but had an average annual incidence only 1/7th that of infants. The incidence rates for all age groups increased consistently between 1982 and 1986. The most impressive relative increases occurred among older adolescents and persons 20 years of age and older. In 1986, 10% of reported cases were in this age group compared to only 5% in 1982. Rates of hospitalization and complications such as pneumonia, seizures, and encephalopathy associated with pertussis were highest in children less than 6 months of age and declined progressively with increasing age.(ABSTRACT TRUNCATED AT 250 WORDS)