Shannon E. MacDonald

The pot calling the kettle black: the extent and type of errors in a computerized immunization registry and by parent report.

BackgroundAccurate classification of children’s immunization status is essential for clinical care, administration and evaluation of immunization programs, and vaccine program research. Computerized immunization registries have been proposed as a valuable alternative to provider paper records or parent report, but there is a need to better understand the challenges associated with their use. This study assessed the accuracy of immunization status classification in an immunization registry as compared to parent report and determined the number and type of errors occurring in both sources.MethodsThis study was a sub-analysis of a larger study which compared the characteristics of children whose immunizations were up to date (UTD) at two years as compared to those not UTD. Children’s immunization status was initially determined from a population-based immunization registry, and then compared to parent report of immunization status, as reported in a postal survey. Discrepancies between the two sources were adjudicated by review of immunization providers’ hard-copy clinic records. Descriptive analyses included calculating proportions and confidence intervals for errors in classification and reporting of the type and frequency of errors.ResultsAmong the 461 survey respondents, there were 60 discrepancies in immunization status. The majority of errors were due to parent report (n = 44), but the registry was not without fault (n = 16). Parents tended to erroneously report their child as UTD, whereas the registry was more likely to wrongly classify children as not UTD. Reasons for registry errors included failure to account for varicella disease history, variable number of doses required due to age at series initiation, and doses administered out of the region.ConclusionsThese results confirm that parent report is often flawed, but also identify that registries are prone to misclassification of immunization status. Immunization program administrators and researchers need to institute measures to identify and reduce misclassification, in order for registries to play an effective role in the control of vaccine-preventable disease.

Addressing nonresponse bias in postal surveys.

Postal surveys are sometimes thought of as a simple option for collecting data in community-based studies; however, nurse researchers must exercise care in appropriately addressing the issue of nonresponse. In particular, both the reporters and the users of such research should look beyond survey response rates when considering nonresponse bias. This article describes the benefits of using postal surveys in public health nursing research, while noting the various potential sources of survey error. Particular attention is directed to the implications of low survey response rates, including decreased power, increased standard error, and nonresponse bias. The belief that increasing response rates will necessarily reduce nonresponse bias is discussed, with an emphasis on the need to identify the reasons for nonresponse and to be judicious in the use of strategies to reduce nonresponse bias. Common response-enhancement strategies are identified, while noting the potential for these strategies to increase nonresponse bias. Assessment of the presence and magnitude of nonresponse bias is discussed, and techniques for postsurvey data adjustment are noted. The need to consider nonresponse bias in designing all phases of the study is highlighted, and is exemplified with a case study.

Neonatal Vitamin K Refusal and Nonimmunization

BACKGROUND: Neonatal Vitamin K prophylaxis is an effective intervention for reducing vitamin K deficiency bleeding. A recently published report of parental refusal of vitamin K prompted an investigation of the prevalence and characteristics of this group, and exploration of whether these same parents were likely to subsequently refuse immunization for their children. METHODS: We conducted a retrospective population-based cohort study of all infants born in Alberta between 2006 and 2012 by using linkage of administrative health data. Risk factors for vitamin K refusal were determined by using Poisson regression. The association between vitamin K refusal and nonimmunization was assessed using relative risk. RESULTS: Among the 282 378 children in the cohort, 99.7% received vitamin K and 0.3% declined. Midwife-assisted deliveries were more likely to be associated with vitamin K refusal compared with physician-attended delivery (risk ratio 8.4, 95% confidence interval [CI] 6.5–11.0). Planned home delivery (risk ratio 4.9, CI 3.8–6.4) or delivery in a birth center (risk ratio 3.6, CI 2.3–5.6) were more likely to result in decline of vitamin K compared with hospital delivery. Vitamin K refusal was associated with a 14.6 (CI 13.9–15.3) higher relative risk of having no recommended childhood vaccines at 15 months. CONCLUSIONS: This is the first population-based study to characterize parents who are likely to decline vitamin K for their infants and whose children are likely to be unimmunized. These findings enable earlier identification of high-risk parents and provide an opportunity to enact strategies to increase uptake of vitamin K and childhood immunizations.

Risk of febrile seizures after first dose of measles–mumps–rubella–varicella vaccine: a population-based cohort study

Background: The combination measles–mumps–rubella–varicella (MMRV) vaccine currently used in Canada (Priorix-Tetra) may increase the risk of febrile seizures relative to the separate vaccines (MMR and varicella) previously administered. We determined the risk of febrile seizure after the first dose of MMRV, as well as any additional risk for children at high risk for seizures because of pre-existing medical conditions. Methods: In this retrospective, population-based cohort study, we compared the risk of seizures after the first dose of MMRV with the risk after same-day administration of separate MMR and varicella vaccines (MMR+V) in children 12 to 23 months of age in the province of Alberta. We deterministically linked vaccination data to health service utilization data for seizures. We used Poisson regression, with adjustment for age and calendar year, to determine the risk for the full cohort and for high-risk children. Results: The risk of seizures 7 to 10 days after vaccination was twice as high with MMRV as with MMR+V (relative risk [RR] 1.99, 95% confidence interval [CI] 1.30–3.05). The excess absolute risk of seizures was 3.52 seizures per 10 000 doses of MMRV relative to MMR+V. In high-risk children, the risk was not differentially higher for MMRV (RR 1.30, 95% CI 0.60–2.79). Interpretation: Despite an increased risk of febrile seizures following MMRV (compared with MMR+V), the absolute level of risk was small. Policy-makers need to balance these findings with the potential benefits of administering the combination vaccine or determine whether the choice of vaccine rests with clinicians and/or parents.

Parental concern about vaccine safety in Canadian children partially immunized at age 2: A multivariable model including system level factors

Children who begin but do not fully complete the recommended series of childhood vaccines by 2 y of age are a much larger group than those who receive no vaccines. While parents who refuse all vaccines typically express concern about vaccine safety, it is critical to determine what influences parents of ‘partially’ immunized children. This case-control study examined whether parental concern about vaccine safety was responsible for partial immunization, and whether other personal or system-level factors played an important role. A random sample of parents of partially and completely immunized 2 y old children were selected from a Canadian regional immunization registry and completed a postal survey assessing various personal and system-level factors. Unadjusted odds ratios (OR) and adjusted ORs (aOR) were calculated with logistic regression. While vaccine safety concern was associated with partial immunization (OR 7.338, 95% CI 4.138– 13.012), other variables were more strongly associated and reduced the strength of the relationship between concern and partial immunization in multivariable analysis (aOR 2.829, 95% CI 1.151 – 6.957). Other important factors included perceived disease susceptibility and severity (aOR 4.629, 95% CI 2.017 – 10.625), residential mobility (aOR 3.908, 95% CI 2.075 – 7.358), daycare use (aOR 0.310, 95% CI 0.144 - 0.671), number of needles administered at each visit (aOR 7.734, 95% CI 2.598 – 23.025) and access to a regular physician (aOR 0.219, 95% CI 0.057 – 0.846). While concern about vaccine safety may be addressed through educational strategies, this study suggests that additional program and policy-level strategies may positively impact immunization uptake.

Exploring the heterogeneity among partially vaccinated children in a population-based cohort.

INTRODUCTION Vaccination status is often categorized as complete or not-complete. This ignores the potentially important heterogeneity in children whose vaccinations are not-complete. We sought to subcategorize not-completely vaccinated children and determine whether characteristics differed among these subgroups. METHODS This retrospective cohort study assessed vaccination status at 2 years of age for 43,965 children in the 2008 Alberta (Canada) birth cohort who were registered with provincial vital statistics records. Children were categorized (based on the five routinely scheduled childhood vaccines) as complete, incomplete, selective, or non-vaccination status. Characteristics derived from administrative health databases were used to determine factors associated with vaccination status. RESULTS Population-level vaccination status at 2 years of age was found to be: 71.1% complete and 28.9% not complete (21.9% incomplete, 2.0% selective, and 5.1% non-vaccinated). Midwife delivery at home, compared to physician delivery in hospital, was strongly associated with non-vaccination status (adjusted odds ratio [aOR] 51.70, 95% CI 37.10-72.10). Factors that might pose barriers to vaccination, such as single marital status (aOR 1.58, 95% CI 1.49-1.67), large number of household children (≥4 vs. 1) (aOR 3.24, 95% CI 2.95-3.54), and multiple household moves (≥3 vs. 0) (aOR 1.69, 95% CI 1.35-2.10), were all strongly associated with incomplete vaccination status. CONCLUSIONS Of the children who were not completely vaccinated at age 2, the vast majority had started but not completed the vaccination series, while a smaller number were selectively vaccinated or not vaccinated at all. Distinct differences are present among these groups that require attention when addressing vaccine coverage.

Methods used for immunization coverage assessment in Canada, a Canadian Immunization Research Network (CIRN) study

ABSTRACT Accurate and complete immunization data are necessary to assess vaccine coverage, safety and effectiveness. Across Canada, different methods and data sources are used to assess vaccine coverage, but these have not been systematically described. Our primary objective was to examine and describe the methods used to determine immunization coverage in Canada. The secondary objective was to compare routine infant and childhood coverage estimates derived from the Canadian 2013 Childhood National Immunization Coverage Survey (cNICS) with estimates collected from provinces and territories (P/Ts). We collected information from key informants regarding their provincial, territorial or federal methods for assessing immunization coverage. We also collected P/T coverage estimates for select antigens and birth cohorts to determine absolute differences between these and estimates from cNICS. Twenty-six individuals across 16 public health organizations participated between April and August 2015. Coverage surveys are conducted regularly for toddlers in Quebec and in one health authority in British Columbia. Across P/Ts, different methodologies for measuring coverage are used (e.g., valid doses, grace periods). Most P/Ts, except Ontario, measure up-to-date (UTD) coverage and 4 P/Ts also assess on-time coverage. The degree of concordance between P/T and cNICS coverage estimates varied by jurisdiction, antigen and age group. In addition to differences in the data sources and processes used for coverage assessment, there are also differences between Canadian P/Ts in the methods used for calculating immunization coverage. Comparisons between P/T and cNICS estimates leave remaining questions about the proportion of children fully vaccinated in Canada.

Immunisation coverage of children in the child welfare system: a systematic review protocol

Introduction Children may be placed in the care of the child welfare system when they require additional supports or intervention to ensure their safety and security. Transitions in living arrangements (eg, home to foster care and return to home) and other difficult circumstances for these children may result in interruptions in routine preventive healthcare, such as childhood immunisations. The purpose of this systematic literature review is to determine whether immunisation coverage is a problem among children in the child welfare system and identify any known supports and/or barriers to vaccine uptake in this population. Methods and analysis This systematic review will encompass published and unpublished primary research studies that assess (A) immunisation coverage of children in the child welfare system, (B) how this coverage compares to the general population and/or children not in the child welfare system, and (C) supports and barriers affecting immunisation status of these children. Vaccines in the recommended childhood immunisation schedule for each study setting will be considered. Medline, Embase, Cochrane Library, CINAHL, SocINDEX and ERIC will be comprehensively searched. We will also search ProQuest dissertations and theses, the Conference Proceedings Citation Index for Science and Social Science & Humanities, and a sample of relevant provincial, national and international websites. References of included studies will be manually searched for relevant studies. English language primary studies from 2000 to current focused on immunisations of children (age 0–17 years) in the child welfare system, in a high-income country, will be included. A narrative analysis of key findings from included studies will be performed and presented. Ethics and dissemination This protocol does not require ethics approval. Planned dissemination includes peer-reviewed publication, conference presentations and briefs for policy makers. Trial registration number This protocol is registered in the PROSPERO International Prospective Register of Systematic Reviews, registration number CRD42016047319.

Coverage and Determinants of Uptake for Privately Funded Rotavirus Vaccine in a Canadian Birth Cohort, 2008-2013.

Background: Rotavirus can lead to serious illness or death, even in developed countries. While vaccination can provide protection, many jurisdictions are still grappling with the issue of whether to introduce a universal publicly funded rotavirus vaccination program. This retrospective population-based study assessed rotavirus vaccine coverage, determinants of uptake, and compliance with the recommended schedule in a Canadian jurisdiction with a privately-funded rotavirus vaccination program. Methods: Analysis of pharmaceutical dispensing, vital statistics, and administrative health data determined vaccine coverage and schedule compliance from 2008 to 2013. Multivariable logistic regression was used to assess characteristics of families purchasing vaccine. Results: Vaccine coverage ranged from 1% to 4% between 2008-2013, with 52% of vaccinated children completing the full vaccine series; 7.9% and 3.8% of children received doses before and after the recommended ages, respectively. Children who received ≥1 doses of the vaccine were more likely to have mothers who were married (adjusted odds ratio [aOR] 1.76, 95% CI1.64-1.88), fewer siblings (aOR 3.44, 95%CI 3.01-3.94), be non-First Nations (aOR 2.29, 95%CI 1.78-2.94), and be born prematurely (aOR 1.32, 95%CI 1.23-1.42). Income was a strong influence in urban areas, but not in rural regions, where coverage was lower overall. Conclusions: Vaccine coverage in a privately-funded model was very low and left high risk populations unprotected. Vaccine series completion and compliance with recommended scheduling was also suboptimal.

The impact of time since vaccination and study design on validity in parental recall of childhood vaccination status in the All Our Families cohort

INTRODUCTION Parental reporting of childhood vaccination status is often used for policy and program evaluation and research purposes. Many factors can bias parental reporting of childhood vaccination status, however, to our knowledge, no analysis has assessed whether time since vaccination impacts reporting accuracy. Therefore, using the Calgary electronic vaccine registry (PHANTIM) as the gold standard, we aimed to test the accuracy of parental reporting of childhood vaccination status at three different time-points since vaccination. METHODS The All Our Families (AOF) cohort study asked parents to report their childs 2, 4, 6, 12 and 18 month vaccines (vaccination time-point) on questionnaires given when the child was 1, 2 and 3 years of age (survey time-point). We linked the AOF parental reporting of vaccination status to the PHANTIM registry and calculated the percent agreement and difference in coverage estimates between PHANTIM and AOF at each vaccination and survey time-point combination. Furthermore, we measured the sensitivity and specificity, and negative (NPV) and positive predictive values (PPV) of parental vaccine recall across time. RESULTS AOF parent reports of coverage rates were consistently higher than the PHANTIM estimates. While we saw significant differences in percent agreement for certain vaccination time-points, we saw no consistent directional difference by survey time-point, suggesting that parental accuracy did not change with time. We found a uniformly high sensitivity across all vaccination and survey time-points, and no consistent patterns in the specificity, PPV and NPV results. CONCLUSION Time since vaccination may not be the most important consideration when designing and implementing a vaccination survey. Other factors that may contribute to the bias associated with parental reporting of vaccination status include the complexity of the vaccine schedule, schedule changes over time, and the wording and structure of the questionnaires.