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Biomedical subjects

Lawrence E Barker

Publications and source records attributed to Lawrence E Barker.

At least 19 recordsLinked to original sources
PubMed2006

Differential effects of the DTaP and MMR vaccine shortages on timeliness of childhood vaccination coverage.

OBJECTIVES: We determined the effect of diphtheria and tetanus toxoids and acellular pertussis vaccine (DTaP) and measles, mumps, rubella (MMR) vaccine shortages on timeliness of the third dose of DTaP (DTaP3), the fourth dose of DTaP (DTaP4), and the first dose of MMR (MMR1) among subgroups of preschool children. METHODS: Data from the 2001 and 2002 National Immunization Surveys were analyzed. Children age-eligible to receive DTaP3, DTaP4, or MMR1 during the shortages were considered subject to the shortage, and those not age-eligible were not subject to the shortage; timeliness of vaccinations was compared. RESULTS: Among children vaccinated only at public clinics, children residing outside metropolitan statistical areas, and children in the Southern Census Region, those age-eligible to receive DTaP4 during the shortage were less likely to be vaccinated by 19 months of age than children not subject to the shortage. CONCLUSIONS: There was notable disparity in the effects of the recent vaccine shortages; children vaccinated only in public clinics, in rural areas, or in the Southern United States were differentially affected by the shortages.

Child, Preschool↗
PubMed2006

Assessment of immunization registry databases as supplemental sources of data to improve ascertainment of vaccination coverage estimates in the national immunization survey.

OBJECTIVE: To evaluate the use of immunization registry data to supplement missing or incomplete vaccination data reported by immunization providers (referred to as "providers" hereafter) in the National Immunization Survey. DESIGN: Cross-sectional, random-digit-dialing, telephone survey to measure vaccination coverage among children aged 19 to 35 months in the United States. SETTING: Four sites with mature (with >67% of provider participation in the area) immunization registries. PARTICIPANTS: Of the 639 children with complete household interviews, interviewers had consent from the respondents for 569 (89.0%) children to contact their providers and for 556 (87.0%) children to contact both providers and registries. MAIN OUTCOME MEASURES: Percentages of children up-to-date for vaccines based on data from providers, registries, and both sources combined. RESULTS: According to provider-reported data, weighted estimates of coverage for the recommended childhood vaccine series 4:3:1:3 at the 4 sites were 65.6%, 78.8%, 81.6%, and 77.0%. According to registry data, these coverage rates were consistently lower: 31.7% (P<.05), 65.4%, 71.9%, and 61.8%, respectively. When all unique vaccine doses were combined from both sources, the pooled 4:3:1:3 coverage rates increased to 72.0%, 92.0%, 88.7%, and 80.2%, respectively. The quality and completeness of vaccination histories from the registries were inconsistent and varied by sites. CONCLUSIONS: Vaccination coverage estimates were the lowest when only registry-reported data were used and were the highest when provider- and registry-reported histories were combined. Although registries enrolled and matched more children, vaccination histories were missing, incomplete, and inconsistent. The quality and completeness of the registry data must be improved and must be comparable across all states before further consideration may be given to supplement or replace the provider-reported National Immunization Survey data.

Child, Preschool↗
PubMed2006

Factors associated with hepatitis a vaccination among children 24 to 35 months of age: United States, 2003.

OBJECTIVES: In 1999, the Advisory Committee on Immunization Practices made recommendations for hepatitis A vaccination of children according to historic rates of hepatitis A incidence in different regions of the country. The objective of this study was to examine hepatitis A vaccination coverage rates among children living in states with different vaccination recommendations and to examine individual characteristics associated with vaccination. METHODS: Hepatitis A vaccination status data were collected for children 24 to 35 months of age through the National Immunization Survey, a telephone survey with health care provider-verified vaccination results. Vaccination status data were collected from children in each of the 50 states and 28 selected urban areas. RESULTS: In 2003, 50.9% (95% confidence interval [CI]: 47.6-54.2%) of children living in 11 states where routine hepatitis A vaccination is recommended had received > or =1 dose, compared with 25.0% (95% CI: 21.8-28.2%) of children in 6 states where vaccination is suggested and 1.4% (95% CI: 1.0-1.8%) of children in 33 states without a recommendation. Coverage was higher among children who lived in urban areas, were Hispanic or American Indian/Alaska Native, or were born to women with less education. CONCLUSIONS: Hepatitis A vaccination is being targeted successfully to children at higher risk of infection; however, overall vaccination coverage remains lower for hepatitis A vaccination, compared with other routine childhood vaccinations.

Child, Preschool↗
PubMed2006

Disparities between white and African-American children in immunization coverage.

INTRODUCTION: A recent study has shown that the national-scale difference in immunization coverage between non-Hispanic white (abbreviated "white") and non-Hispanic African-American (abbreviated "African-American") children aged 19-35 months in the United States has increased by about 1 percentage point annually. We examined how this widening gap differs with geography and income. METHODS: We used data from the National Immunization Survey, 1998-2003, a national telephone survey. We examined differences between white and African-American children in immunization coverage within income groups (at or above versus below the federal poverty level) for each census region (northeast, south, midwest and west). We tested the hypothesis of constant disparity over time. RESULTS: Among households at or above the federal poverty level in the northeast census region, disparity is widening (white coverage minus African-American coverage was -0.5 in 1998 but 15.5 in 2003). Among household at or above the federal poverty level in the midwest census region, disparity is narrowing (white coverage minus African-American coverage was 13.9 in 1998 but 2.5 in 2003). We found no significant evidence of a trend in other groups. CONCLUSIONS: Widening national-level disparity in immunization coverage is primarily attributable to trends in the northeast census region. Addressing the widening disparity in coverage requires new strategies that consider current social and economic contexts.

Black or African American↗
PubMed2005

How do caregivers know when to take their child for immunizations?

BACKGROUND: Childhood vaccinations help reduce and eliminate many causes of morbidity and mortality among children. The objective of this study was to compare 4:3:1:3:3 (4+ doses of diphtheria and tetanus toxoids and pertussis vaccine, 3+ doses of poliovirus vaccine, 1+ doses of measles-containing vaccine, 3+ doses of Haemophilus influenzae type b vaccine, and 3+ doses of hepatitis B vaccine) coverage among children whose caregivers learned by different methods when their child's most recent immunization was needed. METHODS: Between July 2001 and December 2002, a portion of households receiving the National Immunization Survey were asked how they knew when to take the child in for his/her most recent immunization. Responses were post-coded into several categories: 'Doctor/nurse reminder at previous immunization visit', 'Shot card/record', 'Reminder/recall', and 'Other'. Respondents could give more than one answer. Children who did not receive any vaccines, had < or = 1 visits for vaccinations, or whose caregiver did not provide an answer to the question were excluded from analyses. Chi-square analyses were used to compare 4:3:1:3:3 coverage among 19-35 month old children. RESULTS: Children whose caregivers indicated that a doctor/nurse told them at a previous immunization visit when to return for the next immunization had significantly greater 4:3:1:3:3 coverage than those who did not choose the response (77.2% vs. 70.1%, p < 0.01). However, no significant difference in coverage was found between households that did/did not indicate that reminder/recalls (71.0% vs. 75.5%, p = 0.24) helped them remember when to take their child for their most recent immunization visit; only borderline significance was found between those that did/did not choose shot cards (70.6% vs. 76.2%, p = 0.07). CONCLUSION: A doctor or nurse's reminder during an immunization visit of the next scheduled immunization visit effectively encourages caregivers to bring children in for immunizations, providing an inexpensive and easy way to effectively increase immunization coverage.

Caregivers↗
PubMed2005

Measurement of vaccination coverage at age 24 and 19-35 months: a case study of multiple imputation in public health.

AIM: Childhood immunization coverage in the United States (US) is often measured at age 24 months or, in the National Immunization Survey (NIS) at age of interview, which is between 19 and 35 months. This paper compares these standards. METHODS: Data from the NIS is used to compare immunization coverage at time of interview, retrospectively among all children aged 24 or more months at time of interview, and obtained via multiple imputation (with 10 imputations) for all children, both nationally, by state, and by demographic groups. RESULTS: At the national level, the difference between the 19-35 month estimate and the 24 month complete-case estimate was 1.9 percentage points. For most but not all states and subgroups, the 19-35 month estimate was higher than the 24 month complete-case estimate. The difference between vaccination coverage measured at 19-35 months and 24 months ranged from -2.3 to 7.5 percentage points among states. For three states, the difference between the 19-35 month and 24 month complete-case estimate was more than 6 percentage points, in twelve states there was a 4-6 percentage point difference, and in sixteen states a 2-4 percentage point difference. Conversely, five states had higher 24 month complete-case estimates than 19-35 month estimates. CONCLUSION: We found that the coverages at 19-35 and 24 months differ such that they would rarely be adequate surrogates for one another, particularly at a state level. Multiple imputation, which is easily implemented, increases precision of estimates of coverage at age 24 months.

Journal Article↗
PubMed2005

Timeliness of childhood vaccinations in the United States: days undervaccinated and number of vaccines delayed.

CONTEXT: Only 18% of children in the United States receive all vaccinations at the recommended times or acceptably early. OBJECTIVE: To determine the extent of delay of vaccination during the first 24 months of life. DESIGN, SETTING, AND PARTICIPANTS: The 2003 National Immunization Survey was conducted by random-digit dialing of households and mailings to vaccination providers to estimate vaccination coverage rates for US children aged 19 to 35 months. Data for this study were limited to 14,810 children aged 24 to 35 months. MAIN OUTCOME MEASURES: Cumulative days undervaccinated during the first 24 months of life for each of 6 vaccines (diphtheria and tetanus toxoids and acellular pertussis; poliovirus; measles, mumps, and rubella; Haemophilus influenzae type b; hepatitis B; and varicella) and all vaccines combined, number of late vaccines, and risk factors for severe delay of vaccination. RESULTS: Children were undervaccinated a mean of 172 days (median, 126 days) for all vaccines combined during their first 24 months of life. Approximately 34% were undervaccinated for less than 1 month and 29% for 1 to 6 months, while 37% were undervaccinated for more than 6 months. Vaccine-specific undervaccination of more than 6 months ranged from 9% for poliovirus vaccine to 21% for Haemophilus influenzae type b vaccine. An estimated 25% of children had delays in receipt of 4 or more of the 6 vaccines. Approximately 21% of children were severely delayed (undervaccinated for more than 6 months and for > or vaccines). Factors associated with severe delay included having a mother who was unmarried or who did not have a college degree, living in a household with 2 or more children, being non-Hispanic black, having 2 or more vaccination providers, and using public vaccination provider(s). CONCLUSIONS: More than 1 in 3 children were undervaccinated for more than 6 months during their first 24 months of life and 1 in 4 children were delayed for at least 4 vaccines. Standard measures of vaccination coverage mask substantial shortfalls in ensuring that recommendations are followed regarding age at vaccination throughout the first 24 months of life.

Child, Preschool↗
PubMed2005

Ranking states' immunization coverage: an example from the National Immunization Survey.

The National Immunization Survey (NIS) provides state-level estimates of preschool immunization coverage. These coverages are frequently presented in ranked lists, and ranks are frequently over-interpreted. In this paper, we highlight the difficulty in interpreting ranked point estimates. To demonstrate the uncertainty of ranks, parametric bootstrap methods were used to derive 90 per cent confidence intervals for ranks of state vaccination coverage levels among preschool children. We graphically compared states to a reference state. If NIS data are used to rank states, one should consider presenting confidence intervals for rank and the results of comparisons of one state with another graphically.

Child, Preschool↗
PubMed2005

Immunization coverage among Hispanic ancestry, 2003 National Immunization Survey.

BACKGROUND: The Hispanic population is increasing and heterogeneous (Hispanic refers to persons of Spanish, Hispanic, or Latino descent). The objective was to examine immunization rates among Hispanic ancestry for the 4:3:1:3:3 series (> or = 4 doses diphtheria, tetanus toxoids, and pertussis vaccine; > or = 3 doses poliovirus vaccine; > or = 1 doses measles-containing vaccine; > or = 3 doses Haemophilus influenzae type b vaccine; and > or = 3 doses hepatitis B vaccine). METHODS: The National Immunization Survey measures immunization coverage among 19- to 35-month-old U.S. children. Coverage was compared from combined 2001-2003 data among Hispanics and non-Hispanic whites using t-tests, and among Hispanic ancestry using a chi-square test. Hispanics were categorized as Mexican, Mexican American, Central American, South American, Puerto Rican, Cuban, Spanish Caribbean (primarily Dominican Republic), other, and multiple ancestry. RESULTS: Children of Hispanic ancestry increased from 21% in 1999 to 25% in 2003. These Hispanic children were less well immunized than non-Hispanic whites (77.0%, +/-2.1% [95% confidence interval] compared to 82.5%, +/-1.1% (95% CI) > in 2003). Immunization coverage did not vary significantly among Hispanics of varying ancestries (p=0.26); however, there was substantial geographic variability. In some areas, immunization coverage among Hispanics was significantly higher than non-Hispanic whites. CONCLUSIONS: Hispanic children were less well immunized than non-Hispanic whites; however, coverage varied notably by geographic area. Although a chi-square test found no significant differences in coverage among Hispanic ancestries, the range of coverage, 79.2%, +/-5.1% for Cuban Americans to 72.1%, +/-2.4% for Mexican descent, may suggest a need for improved and more localized monitoring among Hispanic communities.

Child, Preschool↗
PubMed2005

Timeliness of childhood immunizations: a state-specific analysis.

OBJECTIVE: We examined the timeliness of vaccine administration among children aged 24 to 35 months for each state of the United States and the District of Columbia. METHODS: We analyzed the timeliness of vaccinations in the 2000-2002 National Immunization Survey. We used a modified Bonferroni adjustment to compare a reference state with all other states. RESULTS: Receipt of all vaccinations as recommended ranged from 2% (Mississippi) to 26% (Massachusetts), with western states having less timeliness than eastern states. CONCLUSIONS: Vaccination coverage measures usually focus on the number of vaccinations accumulated by specified ages. Our analysis of timeliness of administration shows that children rarely receive all vaccinations as recommended. State health departments can use timeliness of vaccinations along with other measures to determine children's susceptibility to vaccine-preventable diseases and to evaluate the quality of vaccination programs. States can use the modified Bonferroni comparison to appropriately compare their results with other states.

Chickenpox Vaccine↗
PubMed2005

Statistical methodology of the National Immunization Survey, 1994-2002.

OBJECTIVES: Since 1994 the National Immunization Survey (NIS) has monitored progress toward the Healthy People 2000 and 2010 vaccination goals. The NIS collects data in two phases: first, a random-digit-dialing (RDD) telephone survey to identify households with children 19-35 months old and, second, a mail survey to vaccination providers to obtain vaccination histories used to estimate vaccination coverage rates. This report reviews the methodologies used in the 1994-2002 NIS to obtain official estimates of vaccination coverage and describes the methodology used for the first three topical modules of the NIS. METHODS: From 1994 to 1997 the NIS used a variation of a two-phase estimator to compensate for missing provider-reported vaccination histories. Between 1998 and 2001 a weighting-class estimator was used. In 2002 and thereafter the weighting-class approach was refined to account for households that do not have telephones and for unvaccinated children. To collect data on immunization-related topics, the NIS sample was randomized among three topical modules: health insurance and ability to pay for vaccinations (HIM); parental knowledge and experiences about vaccinations (PKM); and daycare attendance, breastfeeding practices, and participation in the Special Supplemental Nutrition Program for Women, Infants, and Children (DCM). RESULTS: In 2001 among children with completed RDD interviews, 0.3 percent were entirely unvaccinated. Together, the new nontelephone adjustment and the refinement for unvaccinated children yielded revised estimates that were within 1.5 percentage points of the original estimates obtained using the 1998-2001 methodology. Over the six quarters during which the first three topical modules were fielded (from mid-2001 through 2002), 21,163 children were randomized to the HIM, 3576 to the PKM, and 3511 to the DCM.

Adolescent↗
PubMed2004

Impact of thimerosal-related changes in hepatitis B vaccine birth-dose recommendations on childhood vaccination coverage.

CONTEXT: In July 1999, the longstanding preference to begin hepatitis B vaccination of all US infants at birth was temporarily suspended because of concerns about exposure to mercury contained in the vaccine preservative thimerosal. The suspension was lifted in September 1999 when preservative-free hepatitis B vaccine became available. OBJECTIVE: To determine the effects of changes in recommendations regarding administration of a hepatitis B birth dose on vaccination coverage. DESIGN, SETTING, AND PARTICIPANTS: Cohort analysis of vaccination status of 41,589 US children born before, during, and after the recommendation to suspend the birth dose. MAIN OUTCOME MEASURES: Association between birth cohort and age at receipt of hepatitis B vaccine dose 1, and receipt by 19 months of age of all recommended vaccines. RESULTS: The proportion of US infants who received dose 1 of hepatitis B vaccine at birth declined from 47% among those born 7 to 12 months before the suspension to 11% among those born during the suspension. Birth-dose coverage remained significantly lower in the year after the suspension was lifted (23% in the first 6 months and 33% in months 7-12). Coverage with 3 doses of hepatitis B vaccine by 19 months of age declined from 88% among those born 7 to 12 months before the suspension to 81% among those born during the suspension and 85% among those born in the 6 months after the suspension, but returned to baseline levels for those born 7 to 12 months after the suspension was lifted. These reductions represent 750,000 fewer newborns vaccinated during 2000 compared with 1998, and an excess 182,000 children undervaccinated for hepatitis B at 19 months of age compared with 1998 coverage levels. Coverage with other recommended vaccinations did not decline over this time. CONCLUSIONS: Reductions in hepatitis B vaccine birth-dose coverage persisted after recommendations were made to resume previous newborn vaccination practices. Although the recommendation to complete the series by 19 months of age was never changed, infants born between July and December 1999 were less likely to have completed the series by 19 months, compared with infants born during the previous year. The lack of impact on other vaccinations suggests that public confidence in immunization remained strong.

Cohort Studies↗
PubMed2004

Children who have received no vaccines: who are they and where do they live?

CONTEXT: Each year 2.1 million children 19 to 35 months of age are undervaccinated. Among these are children who have received no vaccinations. Unvaccinated children are at increased risk of acquiring and transmitting vaccine-preventable diseases. OBJECTIVES: To assess whether the characteristics of children with no vaccinations differ from those of undervaccinated children, to monitor trends in the numbers of unvaccinated children, and to identify states with high rates and counties with large numbers of unvaccinated children. DESIGN: A nationally representative probability sample of children 19 to 35 months of age was collected annually between 1995 and 2001. Vaccination histories were ascertained from children's medical providers. Undervaccinated children had received > or =1 dose of diphtheria-tetanus-pertussis, polio, measles, Haemophilus influenzae type b, hepatitis B, or varicella vaccine but were not fully vaccinated. Unvaccinated children were children who were reported as having no medical providers and having received no vaccinations or children whose medical providers reported administering no vaccinations. PARTICIPANTS: A total of 151,720 children sampled between 1995 and 2001, 795 of whom were unvaccinated. RESULTS: Undervaccinated children tended to be black, to have a younger mother who was not married and did not have a college degree, to live in a household near the poverty level, and to live in a central city. Unvaccinated children tended to be white, to have a mother who was married and had a college degree, to live in a household with an annual income exceeding 75,000 dollars, and to have parents who expressed concerns regarding the safety of vaccines and indicated that medical doctors have little influence over vaccination decisions for their children. Unvaccinated children were more likely to be male than female. Annually, approximately 17,000 children were unvaccinated. The largest numbers of unvaccinated children lived in counties in California, Illinois, New York, Washington, Pennsylvania, Texas, Oklahoma, Colorado, Utah, and Michigan. States that allowed philosophical exemptions to laws mandating vaccinations for children as they entered school had significantly higher estimated rates of unvaccinated children. CONCLUSIONS: Unvaccinated children have characteristics that are distinctly different from those of undervaccinated children. Unvaccinated children are clustered geographically, increasing the risk of transmitting vaccine-preventable diseases to both unvaccinated and undervaccinated children.

Attitude to Health↗
PubMed2004

Racial/ethnic disparities in preschool immunizations: United States, 1996-2001.

OBJECTIVES: We examined current racial/ethnic differences in immunization coverage rates among US preschool children. METHODS: Using National Immunization Survey data from 1996 through 2001, we compared vaccination coverage rates between non-Hispanic White, non-Hispanic Black, Hispanic, and Asian preschool children. RESULTS: During the 6-year study period, the immunization coverage gap between White and Black children widened by an average of 1.1% each year, and the gap between White and Hispanic children widened by an average of 0.5% each year. The gap between White and Asian children narrowed by an average of 0.8% each year. CONCLUSIONS: Racial/ethnic disparities in preschool immunization coverage rates have increased significantly among some groups; critical improvements in identifying, understanding, and addressing race/ethnicity-specific health care differences are needed to achieve the Healthy People 2010 goal of eliminating disparities.

Child, Preschool↗
PubMed2004

Insurance status and vaccination coverage among US preschool children.

BACKGROUND: Insurance status has been shown to have an impact on children's use of preventive and acute health services. The objective of this study was to determine the relationship between insurance status and vaccination coverage among US preschool children aged 19 to 35 months. METHODS: We linked data from 2 national telephone surveys, the National Immunization Survey and the National Survey of Early Childhood Health, conducted during the first half of 2000. Children were considered up to date (UTD) when they had received at least 4 diphtheria-tetanus-acellular pertussis/diphtheria-tetanus-pertussis vaccines, 3 poliovirus vaccines, 1 MMR vaccine, 3 Haemophilus influenza vaccines, and 3 hepatitis B vaccines at the time the interview was conducted. RESULTS: Among the 735 children in our study sample, 72% were UTD. The vast majority (94%) reported some type of health insurance at the time of the survey. Children with private insurance were more likely to be UTD (80%) than those with public insurance (56%) or no insurance (64%). In a multivariate analysis that controlled for child's race/ethnicity; household income; maternal age/marital status/educational level; location of usual care; and Special Supplemental Nutrition Program for Women, Infants, and Children participation, insurance was no longer an independent predictor of vaccination. CONCLUSIONS: The disparity in vaccination coverage among publicly, privately, and uninsured children is dramatic, underscoring its importance as a marker for underimmunization, despite the multivariate findings. The Vaccines for Children Program, a partnership between public health and vaccination providers who serve uninsured children and those enrolled in Medicaid, is well suited to target and improve vaccination coverage among these vulnerable children.

Child, Preschool↗
PubMed2003

Predictors of age-appropriate receipt of DTaP dose 4.

BACKGROUND: In the United States, the national childhood immunization schedule calls for children to receive four doses of DTaP (diphtheria and tetanus toxoids and acellular pertussis) vaccine administered at 2, 4, 6, and 15 to 18 months. Dose 4 of DTaP is among the most frequently missed vaccines for children who are not adequately immunized. METHODS: Using the 2001 National Immunization Survey, the effect of the timeliness of the first three DTaP doses was assessed on completion of the four-dose series by age 24 months and on time by age 12 to 18 months. RESULTS: Missing Dose 4 was more prevalent among children who received Dose 3 late (but <16 months) than among children who received Dose 3 on time (24% vs 10%). Similarly, receiving Dose 4 late (or not at all) was more prevalent among children who received Dose 3 late (but <9 months) (39% vs 22%). An invalid Dose 4 was administered to 4.6% of those with Dose 3 late but before 9 months and to 10.6% of those with no Dose 3 before 9 months, compared to 1.2% of those with Dose 3 on time. CONCLUSIONS: Physicians and staff can identify children at risk for missing the fourth DTaP dose or receiving it late by assessing timeliness of receipt of DTaP Dose 3 and implementing steps to ensure that at-risk children receive Dose 4 as recommended.

Diphtheria↗