Steve G. Robison

Priming with Whole-Cell versus Acellular Pertussis Vaccine

About 15 years ago, as part of the pediatric series of vaccines for diphtheria, tetanus, and pertussis, a transition from whole-cell to acellular pertussis vaccine occurred. In this report, investigators from Oregon explore the potential effect of this vaccine switch on subsequent pertussis disease.

Frequency of Alternative Immunization Schedule Use in a Metropolitan Area

OBJECTIVES: Recent studies have described an increase in parental hesitancy regarding vaccines as well as increases in parental adoption of vaccine schedules that delay or limit receipt of recommended vaccines. This study quantifies potential prevalence and trends in alternative schedule compliance by measuring consistent shot-limiting in a metropolitan area of Oregon. METHODS: Retrospective cohort analysis using the Oregon ALERT Immunization Information System to track children born between 2003 and 2009 in the Portland metropolitan area. Joinpoint regression was used to analyze prevalence trends in consistent shot-limiting during that time period. The 2007–2009 Haemophilus influenzae type b vaccine shortage and increased availability of combination vaccines were also examined for their effects on shot-limiting rates. RESULTS: A total of 4502 of 97u2009711 (4.6%) children met the definition of consistent shot-limiters. The proportion of consistent shot-limiters in the population increased from 2.5% to 9.5% between 2006 and 2009. Compared with those with no or episodic limiting, consistent shot-limiters by 9 months of age had fewer injections (6.4 vs 10.4) but more visits when immunizations were administered (4.2 vs 3.3). However, only a small minority of shot-limiters closely adhered to published alternative schedules. CONCLUSIONS: The percentage of children consistently receiving 2 or fewer vaccine injections per visit between birth and age 9 months increased threefold within a 2-year period, suggesting an increase in acceptance of non–Advisory Committee on Immunization Practices vaccine schedules in this geographic area.

Pertussis vaccine performance in an epidemic year — Oregon, 2012

A 2012 pertussis epidemic in Oregon afforded an opportunity to measure vaccine effectiveness; it ranged from 95% (95% confidence interval [CI], 92%-97%) among children 15-47 months of age to 47% (95% CI, 19%-65%) among adolescents 13-16 years of age. In all age groups, pertussis incidence was higher among unimmunized persons.

Sick-Visit Immunizations and Delayed Well-Baby Visits

OBJECTIVE: Giving recommended immunizations during sick visits for minor and acute illness such as acute otitis media has long been an American Academy of Pediatrics/Advisory Committee on Immunization Practice recommendation. An addition to the American Academy of Pediatrics policy in 2010 advised considering whether giving immunizations at the sick visit would discourage making up missed well-baby visits. This study quantifies the potential tradeoff between sick-visit immunizations and well-baby visits. METHODS: This study was a retrospective cohort analysis with a case-control component of sick visits for acute otitis media that supplanted normal well-baby visits at age 2, 4, or 6 months. Infants were stratified for sick-visit immunization, no sick-visit immunization but quick makeup well-baby visits, or no sick-visit immunizations or quick makeup visits. Immunization rates and well-baby visit rates were assessed through 24 months of age. RESULTS: For 1060 study cases, no significant difference was detected in immunization rates or well-baby visits through 24 months of age between those with or without sick-visit immunizations. Thirty-nine percent of infants without a sick-visit shot failed to return for a quick makeup well-baby visit; this delayed group was significantly less likely to be up-to-date for immunizations (relative risk: 0.66) and had fewer well-baby visits (mean: 3.8) from 2 through 24 months of age compared with those with sick-visit shots (mean: 4.7). CONCLUSIONS: The substantial risk that infants will not return for a timely makeup well-baby visit after a sick visit should be included in any consideration of whether to delay immunizations.

The Timing of Pertussis Cases in Unvaccinated Children in an Outbreak Year: Oregon 2012

Objective To assess whether, during a 2012 pertussis outbreak, unvaccinated and poorly vaccinated cases occurred earlier on a community level. Study design Pediatric pertussis among children 2 months to 10 years of age in the Oregon Sentinel Surveillance region during an epidemic starting at the beginning of 2012 were stratified by immunization status, age, zip code, and calendar date of disease onset. Differences in median onset as days between fully or mostly vaccinated, poorly vaccinated, and unvaccinated cases were examined overall and within local zip code areas. Disease clusters also were examined using SatScan analysis. Results Overall, 351 pertussis cases occurred among children aged 2 months to 10 years of age residing in 72 distinct zipcodes. Among unvaccinated or poorly vaccinated cases, their median date of onset was at calendar day 117 (April 26, 2012), whereas for those who were fully or mostly vaccinated the median date of onset was 41 days later, at day 158 (June 6, 2012). Within each local zip code area, the unvaccinated cases were 3.2 times more likely than vaccinated cases to have earlier median dates of onset (95% CI 2.9‐3.6). Conclusion In this outbreak, pertussis cases among unvaccinated children represented an earlier spread of disease across local areas. Controlling outbreaks may require attention to the composition and location of the unvaccinated.

Addressing immunization registry population inflation in adolescent immunization rates.

Objective. While U.S. adolescent immunization rates are available annually at national and state levels, finding pockets of need may require county or sub-county information. Immunization information systems (IISs) are one tool for assessing local immunization rates. However, the presence of IIS records dating back to early childhood and challenges in capturing mobility out of IIS areas typically leads to denominator inflation. We examined the feasibility of weighting adolescent immunization records by length of time since last report to produce more accurate county adolescent counts and immunization rates. Methods. We compared weighted and unweighted adolescent denominators from the Oregon ALERT IIS, along with county-level Census Bureau estimates, with school enrollment counts from Oregons annual review of seventh-grade school immunization compliance for public and private schools. Adolescent immunization rates calculated using weighted data, for the state as a whole, were also checked against comparable National Immunization Survey (NIS) rates. Results. Weighting individual records by the length of time since last activity substantially improved the fit of IIS data to county populations for adolescents. A nonlinear logarithmic (ogive) weight produced the best fit to the school count data of all examined estimates. Overall, the ogive weighted results matched NIS adolescent rates for Oregon. Conclusion. The problem of mobility-inflated counts of teenagers can be addressed by weighting individual records based on time since last immunization. Well-populated IISs can rely on their own data to produce adolescent immunization rates and find pockets of need.

The Concordance of Parent and Child Immunization

Parents’ own immunization behavior is a neglected but strong predictor for their children’s immunizations for both influenza and other recommended immunizations. BACKGROUND: A substantial body of work has related survey-based parental vaccine hesitancy to noncompliant childhood immunization. However little attention has been paid to the connection between parents’ own immunization behavior and the immunizations their children receive. METHODS: Using the Oregon ALERT Immunization Information System, we identified adult caregiver–child pairs for children between 9 months and 17 years of age. The likelihood of adult–child concordance of influenza immunization per influenza season from 2010–2011 through 2014–2015 was assessed. The utility of adult immunization as a predictor was also assessed for other, noninfluenza recommended immunizations for children and adolescents. RESULTS: A total of 450u2009687 matched adult caregiver–child pairs were included in the study. The children of immunizing adults were 2.77 times more likely to also be immunized for seasonal influenza across all seasons (95% confidence interval, 2.74–2.79), with similar results applying within each season. Adult immunization status was also significantly associated with the likelihood of children and adolescents getting other noninfluenza immunizations, such as the human papillomavirus vaccine (HPV). When adults improved their own behavior from nonimmunizing to immunizing across influenza seasons, their children if not immunized in the previous season were 5.44 times (95% confidence interval, 5.35–5.53) more likely to become immunized for influenza. CONCLUSIONS: Children’s likelihood of following immunization recommendations is associated with the immunization behavior of their parents. Encouraging parental immunization is a potential tool for increasing children’s immunization rates.

Changes in Influenza Vaccination Rates After Withdrawal of Live Vaccine

Effects of the US withdrawal of the recommendation for use of LAIVs were assessed in a matched cohort of Oregon children. BACKGROUND: Before the start of the 2016–2017 influenza season, the Advisory Committee on Immunization Practices withdrew its recommendation promoting the use of live attenuated influenza vaccines (LAIVs). There was concern that this might lessen the likelihood that those with a previous LAIV would return for an injectable influenza vaccine (IIV) and that child influenza immunization rates would decrease overall. METHODS: Using Oregons statewide immunization registry, the ALERT Immunization Information System, child influenza immunization rates were compared across the 2012–2013 through 2016–2017 seasons. Additionally, matched cohorts of children were selected based on receipt of either an LAIV or an IIV during the 2015–2016 season. Differences between the IIV and LAIV cohorts in returning for the IIV in the 2016–2017 season were assessed. RESULTS: Overall, influenza immunization rates for children aged 2 to 17 years were unchanged between the 2015–2016 and 2016–2017 seasons. Children aged 3 to 10 with a previous IIV were 1.03 (95% confidence interval, 1.02 to 1.04) times more likely to return for an IIV in 2016-2017 than those with a previous LAIV, whereas children aged 11 to 17 years with a previous IIV were 1.08 (95% confidence interval, 1.05 to −1.09) times more likely to return. CONCLUSIONS: Withdrawal of the LAIV recommendation was not associated with an overall change in child influenza immunization rates across seasons. Children with a previous (2015–2016) IIV were slightly more likely to return during the 2016–2017 season for influenza immunization than those with a previous LAIV.

Do Pertussis Vaccines Protect Against Bordetella parapertussis

We calculated the effectiveness of pertussis vaccine in preventing parapertussis among Oregon children 2 months to 10 years of age using 2 methods. During 2011-2016, the 2 VE methods found 66% (95% CI, 59-75%) and 82% (95% CI, 69-90%) effectiveness against parapertussis. Pertussis vaccine may induce cross-immunity.

Differences in Pertussis Incidence by Income among Oregon Teens during an Outbreak

That disease and poverty are connected is a cornerstone of public health thought. In the case of pertussis, however, it is possible that the expected relationship to poverty is reversed. Grounds exist for considering that increases in income are associated with increases in pertussis rates, both in terms of real risk through social and network features and through the possibility of greater likelihood of care seeking and detection based on income. Using reported adolescent pertussis cases from a 2012 outbreak in Oregon, pertussis incidence rates were determined for areas grouped by zip code into higher, middle, and lower median household income. Adolescents of ages 13–16 years in higher income areas were 2.6 times (95% CI 1.8–3.8) more likely as all others to have reported pertussis during the 2012 outbreak and 3.1 (95% CI 1.4–6.5) times as likely as those in lower income areas. The higher pertussis rates associated with higher income areas were observed regardless of Tdap rate differences. These results suggest that income may be associated with disease risk, likelihood of diagnosis and reporting, or both. Further evaluation of this finding is warranted.