Philip J. Smith

Quantifying bias in a health survey: modeling total survey error in the national immunization survey.

Random-digit-dial telephone surveys are experiencing both declining response rates and increasing under-coverage due to the prevalence of households that substitute a wireless telephone for their residential landline telephone. These changes increase the potential for bias in survey estimates and heighten the need for survey researchers to evaluate the sources and magnitudes of potential bias. We apply a Monte Carlo simulation-based approach to assess bias in the NIS, a land-line telephone survey of 19-35 month-old children used to obtain national vaccination coverage estimates. We develop a model describing the survey stages at which component nonsampling error may be introduced due to nonresponse and under-coverage. We use that model and components of error estimated in special studies to quantify the extent to which noncoverage and nonresponse may bias the vaccination coverage estimates obtained from the NIS and present a distribution of the total survey error. Results indicated that the total error followed a normal distribution with mean of 1.72 per cent(95 per cent CI: 1.71, 1.74 per cent) and final adjusted survey weights corrected for this error. Although small, the largest contributor to error in terms of magnitude was nonresponse of immunization providers. The total error was most sensitive to declines in coverage due to cell phone only households. These results indicate that, while response rates and coverage may be declining, total survey error is quite small. Since response rates have historically been used to proxy for total survey error, the finding that these rates do not accurately reflect bias is important for evaluation of survey data. Published in 2011 by John Wiley & Sons, Ltd.

HPV Vaccination Coverage of Male Adolescents in the United States.

BACKGROUND: In 2011, the Advisory Committee for Immunization Practices (ACIP) recommended routine use human papillomavirus (HPV) vaccine for male adolescents. METHODS: We used the 2013 National Immunization Survey-Teen data to assess HPV vaccine uptake (≥1 dose) and series completion (≥3 doses). Multivariable logistic regression analysis and a predictive marginal model were conducted to identify independent predictors of vaccination among adolescent males aged 13 to 17 years. RESULTS: HPV vaccination coverage with ≥1 dose was 34.6%, and series completion (≥3 doses) was 13.9%. Coverage was significantly higher among non-Hispanic blacks and Hispanics compared with non-Hispanic white male adolescents. Multivariable logistic regression showed that characteristics independently associated with a higher likelihood of HPV vaccination (≥1 dose) included being non-Hispanic black race or Hispanic ethnicity; having mothers who were widowed, divorced, or separated; having 1 to 3 physician contacts in the past 12 months; a well-child visit at age 11 to 12 years; having 1 or 2 vaccination providers; living in urban or suburban areas; and receiving vaccinations from >1 type of facility (P < .05). Having mothers with some college or college education, having a higher family income to poverty ratio, living in the South or Midwest, and receiving vaccinations from all sexually transmitted diseases/school/teen clinics or other facilities were independently associated with a lower likelihood of HPV vaccination (P < .05). CONCLUSIONS: Following recommendations for routine HPV vaccination among male adolescents, uptake in 2013 was low in this population. Increased efforts are needed to improve vaccination coverage, especially for those who are least likely to be vaccinated.

Trends in vaccination coverage disparities among children, United States, 2001–2010☆

INTRODUCTION One of two overarching goals of the Healthy People 2010 initiative was to eliminate health disparities. We evaluate trends in children vaccination coverage disparities by socio-demographic characteristics in the United States from 2001 through 2010. METHODS Disparities in vaccination coverage for the 4:3:1:3:3:1 vaccine series was assessed with National Immunization Survey (NIS) 2001-2010 data. The disparities between two categories of population were independently evaluated yearly from 2001 through 2010. RESULTS In 2001, 10 out of 12 disparities were significant (P-value <0.05). Six disparities were reduced from statistically significant in 2001 to not significant in 2010. Across 2001-2010, 8 disparities narrowed significantly; the average change in disparities per year were negative and ranged from -0.30% to -0.64% (P-value <0.05). CONCLUSIONS Significant success has been achieved in reducing disparities in vaccination coverage for young children among most of the major socio-demographic subpopulations in the United States by 2010.

Who is unlikely to report adverse events after vaccinations to the Vaccine Adverse Event Reporting System (VAERS)

BACKGROUND Healthcare provider (HCP) reporting to the Vaccine Adverse Event Reporting System (VAERS) is important to assuring the safety of U.S. licensed vaccines. HCP awareness of and practices regarding reporting of adverse events following immunization (AEFI) is understudied. METHODS A large, nationally representative sample of U.S. office-based HCP across three occupational groups (physicians, mid-level providers [physician assistants, advanced practice nurses] and nurses) and three primary care practice areas (pediatrics, family medicine, internal medicine) were surveyed utilizing standardized methodology. We assessed HCP familiarity with VAERS, the situations under which they were likely to report an AEFI, and the methods they used and preferred for reporting. We used logistic regression to determine factors associated with HCP not reporting AEFI to VAERS. RESULTS Our survey response rate was 54.9%. The percentage of HCP aware of VAERS (71%) varied by occupation and primary care practice area. About 37% of HCP had identified at least one AEFI with only 17% of these indicating that they had ever reported to VAERS. More serious events were more likely to be reported. Factors associated with HCP not reporting AEFI included: HCP not familiar versus very familiar with filing a paper VAERS report (OR=12.84; p<0.0001), primary care practice area of internal medicine versus pediatrics (OR=4.22; p=0.0005), and HCP not familiar versus very familiar with when it was required to file a VAERS report (OR=5.52; p=0.0013). CONCLUSIONS Specific educational interventions targeted to HCP likely to see AEFI but not currently reporting may improve vaccine safety reporting practices.

An elaboration of theory about preventing outbreaks in homogeneous populations to include heterogeneity or preferential mixing.

The goal of many vaccination programs is to attain the population immunity above which pathogens introduced by infectious people (e.g., travelers from endemic areas) will not cause outbreaks. Using a simple meta-population model, we demonstrate that, if sub-populations either differ in characteristics affecting their basic reproduction numbers or if their members mix preferentially, weighted average sub-population immunities cannot be compared with the proportionally-mixing homogeneous population-immunity threshold, as public health practitioners are wont to do. Then we review the effect of heterogeneity in average per capita contact rates on the basic meta-population reproduction number. To the extent that population density affects contacts, for example, rates might differ in urban and rural sub-populations. Other differences among sub-populations in characteristics affecting their basic reproduction numbers would contribute similarly. In agreement with more recent results, we show that heterogeneous preferential mixing among sub-populations increases the basic meta-population reproduction number more than homogeneous preferential mixing does. Next we refine earlier results on the effects of heterogeneity in sub-population immunities and preferential mixing on the effective meta-population reproduction number. Finally, we propose the vector of partial derivatives of this reproduction number with respect to the sub-population immunities as a fundamentally new tool for targeting vaccination efforts.

Human Papillomavirus Vaccination Coverage Among Girls Before 13 Years: A Birth Year Cohort Analysis of the National Immunization Survey–Teen, 2008-2013

Routine human papillomavirus (HPV) vaccination is recommended at 11 or 12 years by the Advisory Committee on Immunization Practices. National Immunization Survey–Teen data were analyzed to evaluate, among girls, coverage with one or more doses of HPV vaccination, missed opportunities for HPV vaccination, and potential achievable coverage before 13 years. Results were stratified by birth year cohorts. HPV vaccination coverage before 13 years (≥1 HPV dose) increased from 28.4% for girls born in 1995 to 46.8% for girls born in 2000. Among girls born during 1999-2000 who had not received HPV vaccination before 13 years (57.2%), 80.1% had at least 1 missed opportunity to receive HPV vaccination before 13 years. Opportunities to vaccinate for HPV at age 11 to 12 years are missed. Strategies are needed to decrease these missed opportunities for HPV vaccination. This can be facilitated by the administration of all vaccines recommended for adolescents at the same visit.

Trends in early childhood vaccination coverage: progress towards US Healthy People 2010 goals.

OBJECTIVES To evaluate trends in national vaccination coverage from 2000 to 2007 among children aged 19-35 months for at least four doses of diphtheria-tetanus-pertussis vaccine (4+DTaP), three doses of poliovirus vaccine (3+Polio), one dose of measles-mumps-rubella vaccine (1+MMR), three doses of Haemophilus influenzae type b vaccine (3+Hib), three doses of hepatitis B vaccine (3+HepB), one dose of Varicella vaccine (1+Var), and the standard vaccine series of these six vaccines (4:3:1:3:3:1). To predict vaccination coverage levels in 2008-2010 for those vaccines that have not yet reached the Healthy People 2010 coverage targets of 90% for individual vaccines and 80% for the vaccine series. METHODS Data were analyzed for 167,086 children aged 19-35 months in the 2000-2007 National Immunization Survey. Vaccination coverage trends were analyzed with weighted least squares linear regression models. Nonlinear Weibull and logarithmic regression models were fitted to these past results, and extrapolation was used to predict vaccination coverage levels for 4+DTaP, 1+Var, and the 4:3:1:3:3:1 series from 2008 to 2010. RESULTS From 2000 to 2007, observed vaccination coverage increased significantly for four of the six vaccines and the standard vaccine series, and reached the 90% target for 3+Polio, 1+MMR, 3+Hib, and 3+HepB. Increases in coverage were not significant for 1+MMR and 3+Hib; however, coverage for these vaccines was consistently>90% throughout the study period. Both Weibull and logarithmic regression models predicted that coverage with 1+Var and the 4:3:1:3:3:1 series will surpass the 2010 target by 2008, while coverage with 4+DTaP will fall short of the target at 86% in 2010. CONCLUSIONS The United States is well on the way toward reaching most of the Healthy People 2010 objectives for early childhood vaccination coverage. Enhanced efforts are needed to ensure that these trends continue, and to increase coverage with 4+DTaP.

Evaluation of potentially achievable vaccination coverage with simultaneous administration of vaccines among children in the United States

BACKGROUND Routine administration of all age-appropriate doses of vaccines during the same visit is recommended for children by the National Vaccine Advisory Committee (NVAC) and the Advisory Committee on Immunization Practices (ACIP). METHODS Evaluate the potentially achievable vaccination coverage for ≥4 doses of diphtheria and tetanus toxoids and acellular pertussis vaccine (4+DTaP), ≥4 doses of pneumococcal conjugate vaccine (4+PCV), and the full series of Haemophilus influenzae type b vaccine (Hib-FS) with simultaneous administration of all recommended childhood vaccines. Compare the potentially achievable vaccination coverage to the reported vaccination coverage for calendar years 2001 through 2013; by state in the United States and by selected socio-demographic factors in 2013. The potentially achievable vaccination coverage was defined as the coverage possible for the recommended 4+DTaP, 4+PCV, and Hib-FS if missed opportunities for simultaneous administration of all age-appropriate doses of vaccines for children had been eliminated. RESULTS Compared to the reported vaccination coverage, the potentially achievable vaccination coverage for 4+DTaP, 4+PCV, and Hib-FS could have increased significantly (P<0.001), the vaccination coverage would have achieved the 90% target of Healthy People 2020 for the three vaccines beginning in 2005, 2008, and 2011 respectively. In 2013, the potentially achievable vaccination coverage increased significantly across all selected socio-demographic factors, potentially achievable vaccination coverage would have reached the 90% target for more than 51% of the states in the United States. CONCLUSIONS The findings in this study suggest that fully utilization of all opportunities for simultaneous administration of all age-eligible childhood doses of vaccines during the same vaccination visit is a critical strategy for achieving the vaccination coverage target of Healthy People 2020. Encouraging providers to deliver all recommended vaccines that are due at each visit by implementing client reminder and recall systems might decrease missed opportunities for simultaneous administration of childhood vaccines.

Missed opportunities for simultaneous administration of the fourth dose of DTaP among children in the United States

BACKGROUND Simultaneous administration of all age-appropriate doses of vaccines is an effective strategy for raising vaccination coverage. Vaccination coverage for ≥4 dose of DTaP (diphtheria, tetanus toxoids, and acellular pertussis vaccine) among children 19-35months in the United States has not reached the Healthy People 2020 target of 90%. Risk factors for missed opportunities for simultaneous administration of the fourth dose of DTaP have not been investigated. METHODS A missed opportunity for simultaneous administration of the fourth dose of DTaP is defined as the failure to administer an age-eligible fourth dose of DTaP, and during the same age-eligible period for the fourth dose of DTaP other recommended and age-appropriate doses of vaccines are given to children. This study used 2001-2014 National Immunization Survey data to describe the trend in missed opportunities for simultaneous administration of the fourth dose of DTaP from 2001 through 2014, assess the prevalence of children who missed opportunities for simultaneous administration of the fourth dose of DTaP by selected factors, and recognize significant risk factors for missed opportunities for simultaneous administration of the fourth dose of DTaP. RESULTS From 2001 to 2014, the prevalence of missed opportunities for simultaneous administration of the fourth dose of DTaP among children 19-35months in the United States ranged from 5.7% to 9.0%; across 13 factors considered, the prevalence of missed opportunities varied from 3.3% to 22.9%. Children who were late in receiving the first to third dose of DTaP had significantly higher prevalence of missed opportunities for simultaneous administration of the fourth dose of DTaP than children who received these doses on-time, with adjusted prevalence ratios for late vs. on-time of 1.7, 1.6, and 3.2, and all P-value<0.01. CONCLUSIONS Improving on-time vaccination of the third dose of DTaP could substantially reduce missed opportunities for simultaneous administration of the fourth dose of DTaP.

WITHDRAWN: Trends in vaccination coverage disparities among children, United States, 2001–2010

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