The following are pre-publication drafts of articles from the
Morbidity and Mortality Weekly Report dated August 25, 1995. Late-breaking articles, and final
editorial revisions are not included;
therefore, these articles should be considered preliminary, and not
to be released to the public. --CDC
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Disabilities Among Children Aged less than or equal to 17 Years --
United States, 1991-1992
     Disabilities among children result in substantial reductions
in quality of life and are associated with increased dependence on
the health-care and social-service systems. To assess the
prevalence of disabilities and their associated health conditions
among children, CDC reviewed data from the Survey of Income and
Program Participation (SIPP) for 1991-1992, which collected
information about chronic conditions, including the functional
limitations related to those conditions (1,2). This report
summarizes SIPP data for children aged less than or equal to 17
years.
     From October 1991 through January 1992, SIPP collected
information about disabilities during personal household interviews
of a sample (n=97,133 persons in 34,100 households) of the U.S.
civilian, noninstitutionalized population. Measures of disability
were based on definitions from the International Classification of
Impairments, Disabilities, and Handicaps (ICIDH)* (3). The ICIDH
extends the International Classification of Diseases (ICD) to
include the personal and social consequences of diseases. Parents
or legal guardians were asked about disabilities among their
children aged less than or equal to 14 years. Children aged 15-17
years were asked directly about disabilities when they were
available; however, for most children in this age group,
information was obtained from their parents or guardians. For
children reported to have a disability, parents were asked about
the condition(s) that caused the functional limitation. Data were
weighted to calculate national estimates representative of the U.S.
population.
     To ensure that the disability data were comprehensive and
accounted for all developmental stages of children, the SIPP
definitions of disability were varied by age group. For children
aged 0-5 years, disability was defined as 1) limitation in the
usual kind of activities done by most children the same age, or 2)
receipt of therapy or diagnostic services by the child for
developmental needs. For children aged greater than or equal to 6
years, disability was any limitation in the ability to do regular
school work. Additional indicators of disability included, for
children aged 3-14 years, a long-lasting condition that limited the
ability to walk, run, or use stairs, and for children aged 15-17
years, measures of problems in personal care, personal management
(activities of daily living**), and the use of assistive aids
(e.g., wheelchair).
     During 1991-1992, an estimated 48.9 million persons (19.4% of
the total U.S. population of 251.8 million) had a disability; of
these, 3.8 million (7.9%) were aged less than or equal to 17 years
(1). For children aged less than 3 years, the overall estimated
prevalence of disabilities was 2.2%; for those aged 3-5 years,
5.2%; for those aged 6-14 years, 6.3%; and for those aged 15-17
years, 9.3% (Table 1). In all age groups, the prevalence of
disabilities was higher among boys than girls; this sex-specific
difference was greatest in the 6-14-year age group.
     The condition most frequently reported as a cause of
functional limitation among children aged less than or equal to 17
years was learning disability (29.5%), followed by speech problems
(13.1%), mental retardation (6.8%), asthma (6.4%), and mental or
emotional problems or disorders (6.3%) (Table 2).
Reported by: JM McNeil, Bur of the Census, Economics and Statistics
Administration, US Dept of Commerce. Disabilities Prevention
Program; Developmental Disabilities Br, Div of Birth Defects and
Developmental Disabilities, National Center for Environmental
Health; Behavioral Risk Factor Surveillance Br, Office of
Surveillance and Analysis, National Center for Chronic Disease
Prevention and Health Promotion, CDC.
Editorial Note: In the United States, the impact of disabilities is
disproportionately higher among children because disabilities with
onset during childhood account for approximately one third of the
years of disability*** in the U.S. population (4). Improved
characterization of the magnitude and distribution of disabilities
among children is important to identify needed services and to
target appropriate interventions. The findings in this report
further document age and sex variations in the prevalence of
disabilities among children. The increase in the prevalence of
disabilities with advancing age probably reflects the ability to
identify more readily academic or behavioral limitations among
older children and variations in the way educational systems
identify children limited in the ability to do regular school work
(5). Reasons for sex-specific differences are unclear and require
further study.
     The approach used in this report to estimate the prevalence of
disabilities was based on limitations in function resulting from
chronic conditions rather than on the diagnosis of such conditions.
Previous studies may have underestimated the prevalence of
disabilities among children because the definitions were restricted
to certain conditions (6). To improve the precision of estimates of
disability, the SIPP definitions were broadened to include the
functional consequences of chronic conditions. The inclusion of
these functional limitations enables more accurate estimates of the
prevalence of disabilities. However, the SIPP data are subject to
at least two limitations. First, because children living in
institutions or group homes were excluded from the study, the
prevalence of disabilities among children probably is
underestimated. Second, age-group-specific variations in the
definitions of disability limit the basis for comparison across age
groups.
     In SIPP, health conditions associated with disabilities
comprise a combination of diseases (e.g., asthma or diabetes),
impairments (e.g., missing extremities or paralysis), and primary
conditions considered to be disabilities (e.g., mental retardation
or cerebral palsy). Efforts to improve the precision of national
estimates of disabilities among children should distinguish between
those impairments, disabilities, and handicaps that are
consequences of the disabling process. One such effort is the 1999
revision of the ICIDH, which will emphasize measures of disability
and handicap among children (7) and assist in standardizing
collection of information about disabilities among children.
     Improved estimates of the prevalence of disabilities and their
associated health consequences among children are needed to develop
and evaluate prevention strategies. Estimates based on analysis of
data from SIPP can assist public health planners in identifying
primary services for children with disabilities and in projecting
long-range needs of these children. In addition, the linking of
data about primary disabling conditions among children with the
functional consequences of these conditions enables more precise
estimation of costs required to meet the continuing needs of these
children.
References
1. McNeil JM. Americans with disabilities, 1991-1992. Washington,
DC: US Department of Commerce, Economics and Statistics
Administration, Bureau of the Census, 1993. (Current population
reports; series p70, no. 33).
2. CDC. Prevalence of disabilities and associated health
conditions. MMWR 1994;43:730-1,737-9.
3. World Health Organization. International classification of
impairments, disabilities, and handicaps. Geneva: World Health
Organization, 1980.
4. Houk VN, Thacker SB. Program to prevent primary and secondary
disabilities in the United States. Public Health Rep 1989;104:226-31.
5. US Department of Education. 11th Annual report to Congress on
the implementation of the Individuals with Disability Education
Act. Washington, DC: US Department of Education, Office of Special
Education and Rehabilitative Services, Office of Special Education
Programs, 1989.
6. Verbrugge LM. The disability supplement to the 1994-95 National
Health Interview Survey (NHIS-Disability). Hyattsville, Maryland:
US Department of Health and Human Services, Public Health Service,
CDC, NCHS, 1993.
7. Badley EM. An introduction to the concepts and classifications
of the International Classification of Impairments, Disabilities,
and Handicaps. Disabil Rehabil 1993;15:161-78.

* Based on the ICIDH, an impairment is an abnormality of an organ
system, a disability is a person's limitation in function resulting
from an impairment, and a handicap is the social consequence(s) or
disadvantage(s) resulting from impairment and disability that a
person experiences while interacting in the physical and social
environment.
** Ability to 1) "get around inside the home"; 2) "get in and out
of bed or a chair"; 3) "take a bath or shower, dress, and eat;" and
4) "get to and use the toilet."
*** Years of disability are calculated by multiplying the number of
persons with new cases of disabilities by the expected lifespan of
each person with a disability per year. Because years of disability
reflect both prevalence and duration of disability, it is useful in
assessing the impact of preventive interventions.


State and National Vaccination Coverage Levels Among Children Aged
19-35 Months -- United States, April-December 1994
     The National Immunization Survey (NIS) is a single survey
providing state and national estimates of vaccination coverage
levels among children aged 19-35 months. CDC implemented the NIS in
April 1994 as one element of the five-part Childhood Immunization
Initiative (CII) (1), a national strategy to achieve and maintain
high vaccination levels among children during the first 2 years of
life. NIS collects quarterly data from the 50 states, the District
of Columbia, and 27 urban areas considered to have populations at
high risk for undervaccination. This report of initial NIS findings
provides the results of both national and state vaccination
coverage levels for April-December 1994.
     The NIS uses a two-phase sample design. For the first phase,
a quarterly random sample of telephone numbers for each survey area
is called, and a screening questionnaire is administered to locate
households with one or more children aged 19-35 months. Vaccination
information is collected for age-eligible children. All respondents
are requested to refer to written records. During April-December
1994, approximately 1.2 million telephone numbers were called, and
25,247 interviews were completed (an average of 110 interviews per
area per quarter). The overall response rate for eligible
households was 71% (range: 60%-88% among the individual states).
     In the second phase, vaccination information is requested from
health-care providers of children in surveyed households because
parents tend to underestimate the number of doses received for
multiple-dose vaccines and to overestimate coverage for single-dose
vaccines (2,3). Households excluded from phase two include those
that use records indicating their children received all of the
recommended doses for at least four vaccines* because such recorded
histories are highly accurate (CDC, unpublished data, 1995). Based
on these exclusions, 18,479 (73%) households were eligible for
phase two. Of these, vaccination information was obtained from
providers for 7594 (41%) children. The demographic characteristics
and the reported vaccination histories were similar for children in
households with provider information and households with parental
reports only.
     Overall, 57% of the children in the survey had either written
records of having received all of the required doses for at least
four vaccines, or had vaccination information based on provider
records. The data obtained from provider records were used to
improve the accuracy of the vaccination coverage estimates for the
entire sample. Standard two-phase estimation procedures (4) were
used to estimate vaccination coverage for each surveyed area. The
estimates were adjusted using natality data to create a weighted
sample representative of children aged 19-35 months in the United
States; in addition, adjustments were made for nonresponse and for
exclusion of households without a telephone to account for the
finding that children in households without telephones are less
likely to be vaccinated than children in households with a
telephone (CDC, unpublished data, 1995) (5).
     Based on the NIS, among children who were born during May
1991-May 1993 and who were aged 19-35 months (median: 27 months)
when surveyed, estimated vaccination coverage was 75% (confidence
interval [CI]= plus or minus 1.2%) for receipt of at least four
doses of diphtheria and tetanus toxoids and pertussis vaccine
(DTP), three doses of poliovirus vaccine, and one dose of
measles-mumps-rubella vaccine (MMR) (4:3:1 series) (Table 1).
However, except for hepatitis B, coverage levels for each of the
vaccines individually were substantially higher: coverage with
three or more doses of DTP was greater than 90%; coverage for one
dose of MMR, three or more doses of polio, and three or more doses
of Haemophilus influenzae type B vaccine (Hib) ranged from 83% to
89%. The lower overall coverage for the 4:3:1 series was accounted
for primarily by low coverage for the fourth dose of DTP (77%).
     State-specific estimated coverage levels for the 4:3:1 series
ranged from 61% (CI= plus or minus 6.2%) to 88% (CI= plus or minus
4.6%) (Table 2). Coverage levels were less than 65% in three
states, greater than or equal to 85% in three states, and were
higher in the northeastern and southeastern regions (Figure 1).
     To assess the validity of estimates from the NIS, findings
were compared with previously reported data from the National
Health Interview Survey (NHIS) (6,7), a national household survey
of the U.S. civilian, noninstitutionalized population. For January-June 1994, NHIS data had been
supplemented with provider
information in the same manner as in the NIS survey. The estimated
coverage level of 75% in the NIS survey was similar to the 72%
estimate obtained from the NHIS, and vaccine coverage levels for
each individual vaccine (except for hepatitis B) were nearly
identical (Table 1). In addition, estimates of vaccination coverage
derived independently by selected states for 1994 were similar to
those reported in the NIS (CDC, unpublished data, 1995).
Reported by: National Center for Health Statistics; Assessment Br,
Data Management Div, National Immunization Program, CDC.
Editorial Note: The NIS data provide the first current,
population-based, state-specific estimates of vaccination coverage
produced by a standard methodology for the United States. These
findings enable valid comparisons of state efforts to deliver
vaccination services. The NIS has obtained the most reliable
estimates of vaccination coverage through the use of health-care
provider records and the use of data from the NHIS to adjust for
households without telephones. The estimate of the coverage for the
4:3:1 series based on NIS (75%) was substantially higher than that
previously reported through the NHIS (67%), probably reflecting
improvements in the accuracy of both NIS and NHIS data with the
inclusion of information from providers rather than a true increase
in coverage. CDC will continue to assess and improve the quality of
national vaccination data.
     The vaccination coverage rates reported in the NIS and in
recent reports from the NHIS are the highest ever recorded in the
United States. In particular, the findings in the NIS indicate that
the CII goal for 90% coverage with three doses of DTP was exceeded,
and that the 90% coverage goals for polio, measles, and Hib were
nearly attained (1). Coverage for hepatitis B, the vaccine most
recently added to the pediatric schedule, was the lowest because
many children were born before the recommendations for vaccination
were made.
     Coverage for four doses of DTP is the lowest of the three
vaccines included in the combined series. The Advisory Committee on
Immunization Practices recently reaffirmed its recommendation for
a fourth dose of DTP for all children aged 12-18 months (8).
Efforts to ensure timely administration of the fourth dose of DTP
vaccine must be intensified to further reduce the incidence of
pertussis and should include simultaneous administration with other
vaccines recommended for children aged 12-18 months.
     The substantial variation in state-specific coverage levels
for the 4:3:1 series underscores the need for vaccination efforts
targeted at children aged less than 2 years; in addition, more than
one million children still lack one or more doses of the
recommended vaccines. One of the national health objectives for the
year 2000 is to achieve series-complete coverage for at least 90%
of 2-year-old children for all recommended vaccines** (objective
20.11) (9). Implementation of the five-part CII strategy will be
essential to meet this goal and to build a national system that
maintains high coverage levels.
     Potential limitations of NIS include the possible biases
associated with exclusion of households without telephones,
household nonresponse, and inaccurate reporting from households and
small sample sizes for some states. An adjustment for exclusion of
households without telephones was made to account for findings in
the 1992-1993 NHIS that coverage levels for the 4:3:1 series are
approximately 10 percentage points lower among children in
households without telephones (CDC, unpublished data, 1995).
Although provider information was not available for all children,
those children whose providers were not included in the survey were
similar to children whose provider was included, suggesting that
use of provider data did not introduce a bias. In addition,
estimates based on small sample sizes have a larger variance;
future analyses will include data for four quarters, thereby
reducing the size of the sampling error.
     CDC will use the NIS, with data from the NHIS, to evaluate
progress toward national vaccination goals and, because of the
comparability of the information in the NIS, to identify states
with the highest rates (whose programs may be models for other
states) and states with lower rates (which may need special
attention). These coverage estimates are being used to distribute
$33 million in incentive funds, with the greatest funding per fully
vaccinated child to states that achieve the highest levels of
coverage.
References
1. CDC. Reported vaccine-preventable diseases--United States, 1993,
and the Childhood Immunization Initiative. MMWR 1994;43:57-60.
2. Goldstein KP, Kviz FJ, Daum RS. Accuracy of immunization
histories provided by adults accompanying preschool children to a
pediatric emergency department. JAMA 1993;270:2190-4.
3. Valadez JJ, Weld LH. Maternal recall error of child vaccination
status in a developing nation. Am J Public Health 1992:82:120-2.
4. Cochran WG. Double sampling. In: Cochran WG. Sampling
techniques. 3rd ed. New York: John Wiley & Sons, Inc, 1977:327-58.
5. Massey JT, Botman SL. Weighting adjustments for random digit
dialed surveys. In: Groves RM, Biemer PP, Lyberg LE, Massey JT,
Nicholls WL, Waksberg J. Telephone survey methodology. New York:
John Wiley & Sons, Inc, 1988:143-60.
6. CDC. Vaccination coverage of 2-year-old children--United States,
January-March, 1994. MMWR 1995:44:142-3,149-50.
7. CDC. Vaccination coverage levels among children aged 19-35
months--United States, April-June 1994. MMWR 1995:44:396-8.
8. CDC. Recommended childhood immunization schedule--United States,
1995. MMWR 1995; 44(no. RR-5).
9. Public Health Service. Healthy people 2000: national health
promotion and disease prevention objectives--full report, with
commentary. Washington, DC: US Department of Health and Human
Services, Public Health Service, 1991; DHHS publication no.
(PHS)91-50212.

* Vaccines in this series include four doses of diphtheria and
tetanus toxoids and pertussis vaccine (DTP), three doses of
poliovirus vaccine, one dose of measles-mumps-rubella vaccine
(MMR), and three doses of Haemophilus influenzae type B vaccine
(Hib). Children may or may not have received three doses of
hepatitis B vaccine.
** Series-complete coverage of all currently recommended vaccines
include four doses of DTP, three doses of polio, one dose of MMR,
and three doses each of Hib and hepatitis B vaccine.