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Importance: The burden of influenza among young children is high, and influenza vaccination is the primary strategy to prevent the virus and its complications. Less is known about differences in clinical protection following 1 vs 2 doses of initial influenza vaccination., Objectives: To describe patterns of influenza vaccination among young children who receive outpatient care for acute respiratory tract illness in the US and compare vaccine effectiveness (VE) against medically attended laboratory-confirmed influenza by number of influenza vaccine doses received., Design: This test-negative case-control study was conducted in outpatient clinics, including emergency departments, at 5 sites of the US Influenza Vaccine Effectiveness Network during the 2014-2015 through 2017-2018 influenza seasons. The present study was performed from November 5, 2014, to April 12, 2018, during periods of local influenza circulation. Children aged 6 months to 8 years with an acute respiratory tract illness with cough who presented for outpatient care within 7 days of illness onset were included. All children were tested using real-time, reverse-transcriptase polymerase chain reaction for influenza for research purposes., Exposures: Vaccination in the enrollment season with either 1 or 2 doses of inactivated influenza vaccine as documented from electronic medical records, including state immunization information systems., Main Outcomes and Measures: Medically attended acute respiratory tract infection with real-time, reverse-transcriptase polymerase chain reaction testing for influenza., Results: Of 7533 children, 3480 children (46%) were girls, 4687 children (62%) were non-Hispanic white, and 4871 children (65%) were younger than 5 years. A total of 3912 children (52%) were unvaccinated in the enrollment season, 2924 children (39%) were fully vaccinated, and 697 children (9%) were partially vaccinated. Adjusted VE against any influenza was 51% (95% CI, 44%-57%) among fully vaccinated children and 41% (95% CI, 25%-54%) among partially vaccinated children. Among 1519 vaccine-naive children aged 6 months to 2 years, the VE of 2 doses in the enrollment season was 53% (95% CI, 28%-70%), and the VE of 1 dose was 23% (95% CI, -11% to 47%); those who received 2 doses were less likely to test positive for influenza compared with children who received only 1 dose (adjusted odds ratio, 0.57; 95% CI, 0.35-0.93)., Conclusions and Relevance: Consistent with US influenza vaccine policy, receipt of the recommended number of doses resulted in higher VE than partial vaccination in 4 influenza seasons. Efforts to improve 2-dose coverage for previously unvaccinated children may reduce the burden of influenza in this population.

Introduction: A multifaceted intervention to raise influenza vaccination rates was tested among children with asthma., Methods: In a pre/post study design, 18 primary care practices implemented the 4 Pillars Immunization Toolkit along with other strategies. The primary outcome was the difference in influenza vaccination rates at each practice among children with asthma between the baseline year (before the intervention) and at the end of year 2 (after the intervention), both overall and by race (White vs. non-White)., Results: Influenza vaccination rates increased significantly in 13 of 18 practices. The percentage of vaccinated non-White children increased from 46% to 61% (p < .01), and the percentage of vaccinated White children increased from 58% to 65% (p < .001). Likelihood of vaccination was significantly lower for non-White children before the intervention (odds ratio = 0.66; 95% confidence interval = 0.59-0.73; p < .001), but this difference was eliminated after the intervention (odds ratio = 0.95; 95% confidence interval = 0.85-1.05; p = .289)., Discussion: A multi-strategy, evidence-based intervention significantly increased influenza vaccination uptake and reduced racial disparities among children with asthma., (Copyright © 2016 National Association of Pediatric Nurse Practitioners. All rights reserved.)

Background: Few studies have examined the effectiveness of full versus partial vaccination with inactivated trivalent influenza vaccines (IIV3) as defined by the US CDC Advisory Committee on Immunization Practices., Methods: Respiratory swabs were collected from outpatients aged 6 months to 8 years with acute cough for ≤7 days in clinics in 5 states during the 2011-2012 and 2012-2013 influenza seasons. Influenza was confirmed by real-time reverse transcription polymerase chain reaction assay. Receipt of current season IIV3 and up to 4 prior vaccinations was documented from medical records and immunization registries. Using a test-negative design, vaccine effectiveness (VE) was estimated adjusting for age, race/ethnicity, medical conditions, study site and month of enrollment., Results: We did not observe higher VE for children fully versus partially vaccinated with IIV3, as defined by US Advisory Committee on Immunization Practice, although our sample of partially vaccinated children was relatively small. However, among children aged 2-8 years in both seasons and against A(H3N2) and B influenza illness separately, VE point estimates were consistently higher for children who had received 2 doses in the same prior season compared with those without (VE range of 58%-80% vs. 33%-44%, respectively). Across seasons, the odds of A(H3N2) illness despite IIV3 vaccination were 2.4-fold (95% confidence interval: 1.4-4.3) higher among children who had not received 2 doses in the same prior season. We also noted residual protection among unvaccinated children who were vaccinated the previous season (VE range = 36%-40% across outcomes)., Conclusion: Vaccination with IIV3 may provide preventive benefit in subsequent seasons, including possible residual protection if vaccination is missed. Two vaccine doses in the same season may be more effective than alternative priming strategies.

Objective: Influenza vaccination rates among some groups of children remain below the Healthy People 2020 goal of 70%. Multistrategy interventions to increase childhood influenza vaccination have not been evaluated recently., Methods: Twenty pediatric and family medicine practices were randomly assigned to receive the intervention in either year 1 or year 2. This study focuses on influenza vaccine uptake in the 10 year 1 intervention sites during intervention and the following maintenance year. The intervention included the 4 Pillars Immunization Toolkit-a practice improvement toolkit, early delivery of donated vaccine for disadvantaged children, staff education, and feedback on progress. During the maintenance year, practices were not assisted or contacted, except to complete follow-up surveys. Student's t tests assessed vaccine uptake of children aged 6 months to 18 years, and multilevel regression modeling in repeated measures determined variables related to the likelihood of vaccination., Results: Influenza vaccine uptake increased 12.4 percentage points (PP; P < .01) during active intervention and uptake was sustained (+0.4 PP; P > .05) during maintenance, for an average change of 12.7 PP over all sites, increasing from 42.2% at baseline to 54.9% (P < .001) during maintenance. In regression modeling that controlled for age, race, and insurance, likelihood of vaccination was greater during intervention than baseline (odds ratio 1.47; 95% confidence interval 1.44-1.50; P < .001) and greater during maintenance than baseline (odds ratio 1.50; 95% confidence interval 1.47-1.54; P < .001)., Conclusions: In primary care practices, a multistrategy intervention that included the 4 Pillars Immunization Toolkit, early delivery of vaccine, and feedback was associated with significant improvements in childhood influenza vaccination rates that were maintained 1 year after active intervention., (Copyright © 2016 Academic Pediatric Association. All rights reserved.)

Background: Since the 2008 inception of universal childhood influenza vaccination, national rates have risen more dramatically among younger children than older children and reported rates across racial/ethnic groups are inconsistent. Interventions may be needed to address age and racial disparities to achieve the recommended childhood influenza vaccination target of 70%., Purpose: To evaluate an intervention to increase childhood influenza vaccination across age and racial groups., Methods: In 2011-2012, a total of 20 primary care practices treating children were randomly assigned to the intervention and control arms of a cluster randomized controlled trial to increase childhood influenza vaccination uptake using a toolkit and other strategies including early delivery of donated vaccine, in-service staff meetings, and publicity., Results: The average vaccination differences from pre-intervention to the intervention year were significantly larger in the intervention arm (n=10 practices) than the control arm (n=10 practices); for children aged 9-18 years (11.1 pct pts intervention vs 4.3 pct pts control, p<0.05); for non-white children (16.7 pct pts intervention vs 4.6 pct pts control, p<0.001); and overall (9.9 pct pts intervention vs 4.2 pct pts control, p<0.01). In multi-level modeling that accounted for person- and practice-level variables and the interactions among age, race, and intervention, the likelihood of vaccination increased with younger age group (6-23 months); white race; commercial insurance; the practice's pre-intervention vaccination rate; and being in the intervention arm. Estimates of the interaction terms indicated that the intervention increased the likelihood of vaccination for non-white children in all age groups and white children aged 9-18 years., Conclusions: A multi-strategy intervention that includes a practice improvement toolkit can significantly improve influenza vaccination uptake across age and racial groups without targeting specific groups, especially in practices with large percentages of minority children., (Copyright © 2014 American Journal of Preventive Medicine. All rights reserved.)

Purpose: To increase childhood influenza vaccination rates using a toolkit and early vaccine delivery in a randomized cluster trial., Methods: Twenty primary care practices treating children (range for n=536-8183) were randomly assigned to Intervention and Control arms to test the effectiveness of an evidence-based practice improvement toolkit (4 Pillars Toolkit) and early vaccine supplies for use among disadvantaged children on influenza vaccination rates among children 6 months-18 years. Follow-up staff meetings and surveys were used to assess use and acceptability of the intervention strategies in the Intervention arm. Rates for the 2010-2011 and 2011-2012 influenza seasons were compared. Two-level generalized linear mixed modeling was used to evaluate outcomes., Results: Overall increases in influenza vaccination rates were significantly greater in the Intervention arm (7.9 percentage points) compared with the Control arm (4.4 percentage points; P<0.034). These rate changes represent 4522 additional doses in the Intervention arm vs. 1390 additional doses in the Control arm. This effect of the intervention was observed despite the fact that rates increased significantly in both arms - 8/10 Intervention (all P<0.001) and 7/10 Control sites (P-values=0.04 to <0.001). Rates in two Intervention sites with pre-intervention vaccination rates >58% did not significantly increase. In regression analyses, a child's likelihood of being vaccinated was significantly higher with: younger age, white race (Odds ratio [OR]=1.29; 95% confidence interval [CI]=1.23-1.34), having commercial insurance (OR=1.30; 95%CI=1.25-1.35), higher pre-intervention practice vaccination rate (OR=1.25; 95%CI=1.16-1.34), and being in the Intervention arm (OR=1.23; 95%CI=1.01-1.50). Early delivery of influenza vaccine was rated by Intervention practices as an effective strategy for raising rates., Conclusions: Implementation of a multi-strategy toolkit and early vaccine supplies can significantly improve influenza vaccination rates among children in primary care practices but the effect may be less pronounced in practices with moderate to high existing vaccination rates. Clinical trial registry name/number: From Innovation to Solutions: Childhood Influenza/NCT01664793., (Copyright © 2014 Elsevier Ltd. All rights reserved.)