Comparison of COVID-19 and Influenza-Related Outcomes in the United States during Fall-Winter 2022-2023: A Cross-Sectional Retrospective Study

Influenza and COVID-19 contribute significantly to the infectious disease burden during the respiratory season, but their relative burden remains unknown. This study characterizes the frequency and severity of medically attended COVID-19 and influenza during the peak of the 2022-2023 influenza season in the pediatric, adult, and older adult populations and characterizes the prevalence of underlying conditions among patients hospitalized with COVID-19. This cross-sectional analysis included individuals in the Veradigm EHR Database linked to Komodo claims data with a medical encounter between 1 October 2022 and 31 March 2023 (study period). Patients with medical encounters were identified with a diagnosis of COVID-19 or influenza during the study period and stratified based on the highest level of care received with that diagnosis. Among 23,526,196 individuals, there were more COVID-19-related medical encounters than influenza-related encounters, overall and by outcome. Hospitalizations with COVID-19 were more common than hospitalizations with influenza overall (incidence ratio = 4.6) and in all age groups. Nearly all adults hospitalized with COVID-19 had at least one underlying medical condition, but 37.1% of 0-5-year-olds and 25.0% of 6-17-year-olds had no underlying medical conditions. COVID-19 was associated greater burden than influenza during the peak of the 2022-2023 influenza season.

Comparative Effectiveness of Bivalent (Original/Omicron BA.4/BA.5) COVID-19 Vaccines in Adults

The emergence of Omicron variants coincided with declining vaccine-induced protection against SARS-CoV-2. Two bivalent mRNA vaccines, mRNA-1273.222 (Moderna) and BNT162b2 Bivalent (Pfizer-BioNTech), were developed to provide greater protection against the predominate circulating variants by including mRNA that encodes both the ancestral (original) strain and BA.4/BA.5. We estimated their relative vaccine effectiveness (rVE) in preventing COVID-19-related outcomes in the US using a nationwide dataset linking primary care electronic health records and pharmacy/medical claims data. The study population (aged ≥18 years) received either vaccine between 31 August 2022 and 28 February 2023. We used propensity score weighting to adjust for baseline differences between groups. We estimated the rVE against COVID-19-related hospitalizations (primary outcome) and outpatient visits (secondary) for 1,034,538 mRNA-1273.222 and 1,670,666 BNT162b2 Bivalent vaccine recipients, with an adjusted rVE of 9.8% (95% confidence interval: 2.6-16.4%) and 5.1% (95% CI: 3.2-6.9%), respectively, for mRNA-1273.222 versus BNT162b2 Bivalent. The incremental relative effectiveness was greater among adults ≥ 65; the rVE against COVID-19-related hospitalizations and outpatient visits in these patients was 13.5% (95% CI: 5.5-20.8%) and 10.7% (8.2-13.1%), respectively. Overall, we found greater effectiveness of mRNA-1273.222 compared with the BNT162b2 Bivalent vaccine in preventing COVID-19-related hospitalizations and outpatient visits, with increased benefits in older adults.

Relative Effectiveness of BNT162b2, mRNA-1273, and Ad26.COV2.S Vaccines and Homologous Boosting in Preventing COVID-19 in Adults in the US

Background

Few head-to-head comparisons have been performed on the real-world effectiveness of coronavirus disease 2019 (COVID-19) booster vaccines. We evaluated the relative effectiveness (rVE) of a primary series of mRNA-1273 vs BNT162b2 and Ad26.COV2.S and a homologous mRNA booster against any medically attended, outpatient, and hospitalized COVID-19.

Methods

A data set linking primary care electronic medical records with medical claims data was used for this retrospective cohort study of US patients age ≥18 years vaccinated with a primary series between February and October 2021 (Part 1) and a homologous mRNA booster between October 2021 and January 2022 (Part 2). Adjusted hazard ratios (HRs) were derived from 1:1 matching adjusted across potential covariates. rVE was (1 - HR_adjusted) × 100. Additional analysis was performed across regions and age groups.

Results

Following adjustment, Part 1 rVE for mRNA-1273 vs BNT162b2 was 23% (95% CI, 22%-25%), 23% (95% CI, 22%-25%), and 19% (95% CI, 14%-24%), while the rVE for mRNA-1273 vs Ad26.COV2.S was 50% (95% CI, 48%-51%), 50% (95% CI, 48%-52%), and 57% (95% CI, 53%-61%) against any medically attended, outpatient, and hospitalized COVID-19, respectively. The adjusted rVE in Part 2 for mRNA-1273 vs BNT162b2 was 14% (95% CI, 10%-18%), 13% (95% CI, 8%-17%), and 19% (95% CI, 1%-34%) against any medically attended, outpatient, and hospitalized COVID-19, respectively. rVE against medically attended COVID-19 was higher in adults age ≥65 years (35%; 95% CI, 24%-47%) than in those age 18-64 years (13%; 95% CI, 9%-17%) after the booster.

Conclusions

In this study, mRNA-1273 was more effective than BNT162b2 or Ad26.COV2.S following a primary series during the Delta-dominant period and more effective than BNT162b2 as a booster during the Omicron-dominant period.

Parental Attitudes and Perceptions of Support after Brief Clinician Intervention Predict Intentions to Accept the Adjuvanted Seasonal Influenza Vaccination: Findings from the Pediatric Influenza Vaccination Optimization Trial (PIVOT)-I

Adjuvanted trivalent influenza vaccine (aTIV) provides enhanced protection against seasonal influenza in children compared with nonadjuvanted trivalent influenza vaccine (TIV). This prospective cohort study assessed parental attitudes, beliefs, and intentions to vaccinate their infants aged 6-23 months with aTIV. Parents were surveyed before and after routine healthy baby visits, and post clinician interaction results were analyzed using multivariable logistic regression. Physicians at 15 community practice clinics and nurses at 3 public health clinics participated; 207 parents were surveyed. After clinician consultation, most parents considered immunization with aTIV to be safe (72.9%), effective (69.6%), and important (69.0%); most perceived support for vaccination from significant others (62.8%) and clinicians (81.6%); and 66.6% intended to vaccinate their infant with aTIV. Parental attitudes toward vaccinating their infant with aTIV were strongly correlated with perceptions of vaccine safety, efficacy, and importance, and these represented the strongest influence on intentions to vaccinate (odds ratio (OR) 79.25; 95% confidence interval (CI) 6.05-1037.50). Parental intentions were further influenced by perceived strength of clinician recommendation (OR 4.55, 95% CI 1.38-15.06) and social support for vaccination (OR 3.46, 95% CI 0.50-24.13). These findings may inform clinician approaches to parental education to ensure optimal seasonal pediatric influenza vaccination.

Relative Effectiveness of Cell-Based Versus Egg-Based Quadrivalent Influenza Vaccines in Adults During the 2019-2020 Influenza Season in the United States

Background

Mutations occurring during egg-based influenza vaccine production may affect vaccine effectiveness. The mammalian cell-based quadrivalent inactivated influenza vaccine (IIV4c) demonstrated improved protection relative to egg-based vaccines in prior seasons. This study estimated the relative vaccine effectiveness (rVE) of IIV4c versus standard-dose egg-based quadrivalent inactivated influenza vaccine (IIV4e) in preventing influenza-related medical encounters (IRMEs) in the 2019–2020 US influenza season.

Methods

This retrospective cohort study was conducted using a dataset linking electronic medical records with medical and pharmacy claims data among individuals ≥18 years vaccinated with IIV4c or IIV4e during 2019–2020. A doubly robust inverse probability of treatment weighting model was used to obtain odds ratios (ORs) adjusted for age, sex, race, ethnicity, region, vaccination week, health status, frailty, and baseline healthcare resource utilization. rVE was calculated by (1 – OR) × 100. An exploratory analysis evaluated IRMEs in inpatient and outpatient settings separately.

Results

The final study cohort included 1 499 215 IIV4c and 4 126 263 IIV4e recipients ≥18 years of age. Fewer IRMEs were reported in individuals with recorded IIV4c versus IIV4e. The rVE for IIV4c versus IIIV4e for any IRME was 9.5% (95% confidence interval [CI], 7.9%–11.1%). Inpatient and outpatient rVEs were 5.7% (95% CI, 2.1%–9.2%) and 11.4% (95% CI, 9.5%–13.3%), respectively. In age subgroup analyses, rVEs favored IIV4c except in adults aged ≥65 years.

Conclusions

Adults vaccinated with IIV4c had a lower risk of IRMEs versus IIV4e recipients in the 2019–2020 US influenza season. These results support IIV4c as a potentially more effective public health measure against influenza than egg-based vaccines.

Relative Effectiveness of Cell-based Versus Egg-based Quadrivalent Influenza Vaccines in Children and Adolescents in the United States During the 2019-2020 Influenza Season

BACKGROUND

Egg-based influenza vaccine production can lead to the accumulation of mutations that affect antigenicity. The mammalian cell-based inactivated quadrivalent influenza vaccine (IIV4c) may improve effectiveness compared with egg-based vaccines. This study estimated the relative vaccine effectiveness (rVE) of IIV4c versus egg-based inactivated quadrivalent influenza vaccine (IIV4e) in preventing influenza-related medical encounters (IRME) among children and adolescents during the 2019-2020 US influenza season.

METHODS

This retrospective cohort study used a dataset linking primary and specialty care electronic medical records with medical and pharmacy claims data from US residents 4 through 17 years of age vaccinated with IIV4c or IIV4e during the 2019-2020 influenza season. Odds ratios (ORs) were derived from a doubly robust inverse probability of treatment-weighted approach adjusting for age, sex, race, ethnicity, region, index week, health status and two proxy variables for healthcare accessibility and use. Adjusted rVE was estimated by (1-OR adjusted )*100, and an exploratory analysis evaluated IRMEs separately for outpatient and inpatient settings.

RESULTS

The final study cohort included 60,480 (IIV4c) and 1,240,990 (IIV4e) vaccine recipients. Fewer IRMEs were reported in subjects vaccinated with IIV4c than IIV4e. The rVE for IIV4c versus IIV4e was 12.2% [95% confidence interval (CI): 7.5-16.6] for any IRME and 14.3% (9.3-19.0) for outpatient IRMEs. Inpatient IRMEs were much less frequent, and effectiveness estimates were around the null.

CONCLUSIONS

Fewer IRMEs occurred in pediatric subjects vaccinated with IIV4c versus IIV4e. These results support the greater effectiveness of IIV4c over IIV4e in this population during the 2019-2020 US influenza season.

Analysis of Myocarditis Among 252 Million mRNA-1273 Recipients Worldwide

BACKGROUND

Growing evidence indicates a causal relationship between SARS-CoV-2 infection and myocarditis. Post-authorization safety data have also identified myocarditis as a rare safety event following mRNA COVID-19 vaccination, particularly among adolescent and young-adult males after dose 2. We further evaluated the potential risk by querying the Moderna global safety database for myocarditis/myopericarditis reports among mRNA-1273 recipients worldwide.

METHODS

Myocarditis/myopericarditis reports from 18 December 2020 to 15 February 2022 were reviewed and classified. The reported rate after any known mRNA-1273 dose was calculated according to age and sex, then compared with a population-based incidence rate to calculate observed-to-expected rate ratios (RRs).

RESULTS

During the study period, 3017 myocarditis/myopericarditis cases among 252 million mRNA-1273 recipients who received at least 1 dose were reported to the Moderna global safety database. The overall reporting rate was 9.23 per 100 000 person-years, which was similar to the expected reference rate (9.0 cases per 100 000 person-years; RR [95% confidence interval (CI)], 1.03 [.97-1.08]). When stratified by sex and age, observed rates were highest for males aged <40 years, particularly those 18-24 years (53.76 per 100 000 person-years), which was higher than expected (RR [95% CI], 3.10 [2.68-3.58]). When considering only cases occurring within 7 days of a known dose, the observed rate was highest for males aged 18-24 years after dose 2 (4.23 per 100 000 doses administered).

CONCLUSIONS

Myocarditis/myopericarditis rates were not higher than expected for the overall population of mRNA-1273 recipients but were higher than expected in males aged 18-24 years, with most cases occurring 7 days after dose 2.

Relative Effectiveness of MF59® Adjuvanted Trivalent Influenza Vaccine Versus Non-Adjuvanted Vaccines During the 2019-2020 Influenza Season

Background

Age-related immunosenescence may impair the immune response to vaccination in older adults. Adjuvanted influenza vaccines are designed to overcome immune senescence in older adults. This study estimated the relative vaccine effectiveness (rVE) of MF59®-adjuvanted trivalent inactivated influenza vaccine (aIIV3) versus egg-derived quadrivalent inactivated influenza vaccine (IIV4e) and high-dose trivalent inactivated influenza vaccine (HD-IIV3) in preventing influenza-related medical encounters in the 2019-2020 US season.

Methods

This retrospective cohort study used electronic medical records linked to pharmacy and medical claims data. The study population included adults age ≥65 years with a record of aIIV3, IIV4e, or HD-IIV3 vaccination. A doubly robust inverse probability of treatment weighting model was used to derive adjusted odds ratios (OR). rVE was calculated by (1–ORadjusted)*100 and was determined overall and separately for age subgroups. An exploratory analysis evaluated the outcome separately in inpatient and outpatient settings.

Results

Subjects received aIIV3 (n=936,508), IIV3e (n=651,034), and HD-IIV3 (n=1,813,819) and influenza-related medical encounters were recorded in 0.5%, 0.9%, 0.7% of each cohort, respectively. Overall, rVE of aIIV3 was 27.5% (95% CI, 24.4 to 30.5) versus IIV4e and 13.9% (95% CI 10.7 to 17.0) vs versus HD-IIV3. aIIV3 had a more favorable rVE in inpatient and outpatient settings. Findings remained consistent across age subgroups and during alternative seasonal dates.

Conclusions

Adults ≥65 years vaccinated with aIIV3 had fewer influenza-related medical encounters compared with IIV4e or HD-IIV3 during the 2019-2020 US influenza season.

Relative Effectiveness of Adjuvanted Trivalent Inactivated Influenza Vaccine Versus Egg-derived Quadrivalent Inactivated Influenza Vaccines and High-dose Trivalent Influenza Vaccine in Preventing Influenza-related Medical Encounters in US Adults ≥ 65 Years During the 2017-2018 and 2018-2019 Influenza Seasons

Background

The effectiveness of standard, egg-derived quadrivalent influenza vaccines (IIV4) may be reduced in adults ≥65 years of age, largely because of immunosenescence. An MF59-adjuvanted trivalent influenza vaccine (aIIV3) and a high-dose trivalent influenza vaccine (HD-IIV3) offer older adults enhanced protection versus standard vaccines. This study compared the relative effectiveness of aIIV3 with IIV4 and HD-IIV3 in preventing influenza-related medical encounters over 2 US influenza seasons.

Methods

This retrospective cohort study included US patients ≥65 years vaccinated with aIIV3, IIV4, or HD-IIV3. The outcome of interest was the occurrence of influenza-related medical encounters. Data were derived from a large dataset comprising primary and specialty care electronic medical records linked with pharmacy and medical claims. Adjusted odds ratios (OR) were derived from an inverse probability of treatment-weighted sample adjusted for age, sex, race, ethnicity, geographic region, vaccination week, and health status. Relative vaccine effectiveness (rVE) was determined using the formula (% VE = 1 – OR_adjusted) × 100.

Results

In 2017–2018, cohorts included: aIIV3, n = 524 223; IIV4, n = 917 609; and HD-IIV3, n = 3 377 860. After adjustment, 2017–2018 rVE of aIIV3 versus IIV4 was 18.2 (95% confidence interval [CI], 15.8–20.5); aIIV3 vs. HD-IIV3 was 7.7 (95% CI, 2.3–12.8). In 2018–2019, cohorts included: aIIV3, n = 1 031 145; IIV4, n = 915 380; HD-IIV3, n = 3 809 601, with adjusted rVEs of aIIV3 versus IIV4 of 27.8 (95% CI, 25.7–29.9) and vs. HD-IIV3 of 6.9 (95% CI, 3.1–10.6).

Conclusion

In the 2017–2018 and 2018–2019 influenza seasons in the United States, aIIV3 demonstrated greater reduction in influenza-related medical encounters than IIV4 and HD-IIV3 in adults ≥65 years.

Relative Effectiveness of the Cell-derived Inactivated Quadrivalent Influenza Vaccine Versus Egg-derived Inactivated Quadrivalent Influenza Vaccines in Preventing Influenza-related Medical Encounters During the 2018-2019 Influenza Season in the United States

Background

The cell-propagated inactivated quadrivalent influenza vaccine (ccIIV4) may offer improved protection in seasons where egg-derived influenza viruses undergo mutations that affect antigenicity. This study estimated the relative vaccine effectiveness (rVE) of ccIIV4 versus egg-derived inactivated quadrivalent influenza vaccine (eIIV4) in preventing influenza-related medical encounters in the 2018–2019 US season.

Methods

A dataset linking primary care electronic medical records with medical claims data was used to conduct a retrospective cohort study among individuals ≥ 4 years old vaccinated with ccIIV4 or eIIV4 during the 2018–2019 season. Adjusted odds ratios (ORs) were derived from a doubly robust inverse probability of treatment-weighted approach adjusting for age, sex, race, ethnicity, geographic region, vaccination week, and health status. rVE was estimated by (1 – OR) × 100 and presented with 95% confidence intervals (CI).

Results

Following the application of inclusion/exclusion criteria, the study cohort included 2 125 430 ccIIV4 and 8 000 903 eIIV4 recipients. Adjusted analyses demonstrated a greater reduction in influenza-related medical encounters with ccIIV4 versus eIIV4, with the following rVE: overall, 7.6% (95% CI, 6.5–8.6); age 4–17 years, 3.9% (95% CI, .9–7.0); 18–64 years, 6.5% (95% CI, 5.2–7.9); 18–49 years, 7.5% (95% CI, 5.7–9.3); 50–64 years, 5.6% (95% CI, 3.6–7.6); and ≥65 years, –2.2% (95% CI, –5.4 to .9).

Conclusions

Adjusted analyses demonstrated statistically significantly greater reduction in influenza-related medical encounters in individuals vaccinated with ccIIV4 versus eIIV4 in the 2018–2019 US influenza season. These results support ccIIV4 as a potentially more effective public health measure against influenza than an egg-based equivalent.

Effectiveness of the Adjuvanted Influenza Vaccine in Older Adults at High Risk of Influenza Complications

MF59^®-adjuvanted trivalent inactivated influenza vaccine (aIIV3) and high-dose trivalent inactivated influenza vaccine (HD-IIV3) elicit an enhanced immune response in older adults compared to standard, quadrivalent inactivated influenza vaccines (IIV4). We sought to determine the relative vaccine effectiveness (rVE) of aIIV3 versus IIV4 and HD-IIV3 in preventing influenza-related medical encounters in this retrospective cohort study involving adults ≥65 years with ≥1 health condition during the 2017-2018 and 2018-2019 influenza seasons. Data were obtained from primary and specialty care electronic medical records linked with pharmacy and medical claims. Adjusted odds ratios (OR) were derived from an inverse probability of treatment-weighted sample adjusted for age, sex, race, ethnicity, geographic region, vaccination week, and health status. rVE was determined using the formula (% rVE = 1 - OR_adjusted) × 100. Analysis sets included 1,755,420 individuals for the 2017-2018 season and 2,055,012 for the 2018-2019 season. Compared to IIV4, aIIV3 was 7.1% (95% confidence interval 3.3-10.8) and 20.4% (16.2-24.4) more effective at preventing influenza-related medical encounters in the 2017-2018 and 2018-2019 seasons, respectively. Comparable effectiveness was observed with HD-IIV3 across both seasons. Our results support improved effectiveness of aIIV3 vs IIV4 in a vulnerable population of older adults at high risk of influenza and its complications.

Relative Effectiveness of the Cell-Cultured Quadrivalent Influenza Vaccine Compared to Standard, Egg-derived Quadrivalent Influenza Vaccines in Preventing Influenza-like Illness in 2017-2018

Background

Influenza antigens may undergo adaptive mutations during egg-based vaccine production. In the 2017–2018 influenza season, quadrivalent, inactivated cell-derived influenza vaccine (ccIIV4) vaccine was produced using A(H3N2) seed virus propagated exclusively in cell culture, thus lacking egg adaptive changes. This United States study estimated relative vaccine effectiveness (rVE) of ccIIV4 vs egg-derived quadrivalent vaccines (egg-derived IIV4) for that season.

Methods

Vaccination, outcome, and covariate data were ascertained retrospectively from a electronic medical record (EMR) dataset and analyzed. The study cohort included patients ≥ 4 years of age. rVE was estimated against influenza-like illness (ILI) using diagnostic International Classification of Diseases, Ninth or Tenth Revision codes. The adjusted odds ratios used to derive rVE estimates were estimated from multivariable logistic regression models adjusted for age, sex, race/ethnicity, geographic region, and health status.

Results

Overall, 92 187 individuals had a primary care EMR record of ccIIV4 and 1 261 675 had a record of egg-derived IIV4. In the ccIIV4 group, 1705 narrowly defined ILI events occurred, and 25 645 occurred in the standard egg-derived IIV4 group. Crude rVE was 9.2% (95% confidence interval [CI], 4.6%–13.6%). When adjusted for age, sex, health status, comorbidities, and geographic region, the estimated rVE changed to 36.2% (95% CI, 26.1%–44.9%).

Conclusions

ccIIV4, derived from A(H3N2) seed virus propagated exclusively in cell culture, was more effective than egg-derived IIV4 in preventing ILI during the 2017–2018 influenza season. This result suggests that cell-derived influenza vaccines may have greater effectiveness than standard egg-derived vaccines.

Effectiveness of the Cell-Derived Inactivated Quadrivalent Influenza Vaccine in Individuals at High Risk of Influenza Complications in the 2018-2019 United States Influenza Season

Background

Higher rates of influenza-related morbidity and mortality occur in individuals with underlying medical conditions. To improve vaccine effectiveness, cell-based technology for influenza vaccine manufacturing has been developed. Cell-derived inactivated quadrivalent influenza vaccines (cIIV4) may improve protection in seasons in which egg-propagated influenza viruses undergo mutations that affect antigenicity. This study aimed to estimate the relative vaccine effectiveness (rVE) of cIIV4 versus egg-derived inactivated quadrivalent influenza vaccines (eIIV4) in preventing influenza-related medical encounters in individuals with underlying medical conditions putting them at high risk of influenza complications during the 2018-2019 US influenza season.

Methods

An integrated dataset, linking primary care electronic medical records with claims data, was used to conduct a retrospective cohort study among individuals aged ≥4 years, with ≥1 health condition, vaccinated with cIIV4 or eIIV4 during the 2018-2019 season. Adjusted odds ratios (ORs) were derived using a doubly robust inverse probability of treatment-weighting (IPTW) model, adjusting for age, sex, race, ethnicity, geographic region, vaccination week, and health status. Relative vaccine effectiveness was estimated by (1 - OR) × 100 and presented with 95% confidence intervals (CIs).

Results

The study cohort included 471 301 cIIV4 and 1 641 915 eIIV4 recipients. Compared with eIIV4, cIIV4 prevented significantly more influenza-related medical encounters among individuals with ≥1 health condition (rVE, 13.4% [95% CI, 11.4%-15.4%]), chronic pulmonary disease (rVE, 18.7% [95% CI, 16.0%-21.3%]), and rheumatic disease (rVE, 11.8% [95% CI, 3.6%-19.3%]).

Conclusions

Our findings support the use of cIIV4 in individuals ≥4 years of age at high risk of influenza complications and provide further evidence supporting improved effectiveness of cIIV4 compared with eIIV4.

LB-2. Relative Effectiveness of aIIV3 versus IIV4 and HD-IIV3 In Preventing Influenza-Related Medical Encounters in Adults ≥65 Years of Age at High Risk for Influenza Complications During the U.S. 2017–2018 and 2018–2019 Influenza Seasons

Background

Individuals with health conditions have shown higher rates of influenza-related morbidity and mortality compared to healthy individuals and are often prioritized for influenza vaccination. However, vaccination with egg-derived standard quadrivalent inactivated influenza vaccines (IIV4) has shown to be less effective in adults ≥65 years of age largely due to immunosenecence. Two enhanced vaccines, the MF59®-adjuvanted trivalent inactivated influenza vaccine (aIIV3) and a high-dose trivalent inactivated influenza vaccine (HD-IIV3), were developed to provide adults ≥65 years with increased protection. The objective of this study was to determine the relative vaccine effectiveness (rVE) of aIIV3 versus IIV4 and HD-IIV3 in preventing influenza-related medical encounters in high-risk adults ≥65 years.

Methods

A retrospective cohort study was conducted among adults ≥65 years with ≥1 health condition with a record of receiving either aIIV3, IIV4 or HD-IIV3 in the 2017–18 or 2018–19 influenza seasons. Patient-level electronic medical records linked to pharmacy and medical claims were used to ascertain exposure, outcome and covariate information. The primary outcome was influenza-related medical encounters in primary care and hospital (ICD-10 codes J09*–J11*). Inverse probability of treatment weighting was used to obtain odds ratios (ORs) adjusted for age, sex, race, ethnicity, geographic region, comorbidities and week of vaccination for each health condition. rVE was determined using the formula (1-OR)*100 and reported with 95% confidence intervals (CI).

Results

Overall, 1,755,420 individuals with ≥1 health condition were included for analysis in the 2017–18 season and 2,055,012 individuals in the 2018–19 season. In both seasons, high-risk subjects who received aIIV3 had statistically significantly greater reduction in influenza-related medical encounters as compared to IIV4 (Table 1). Non-statistically significant estimates preclude definitive conclusions for comparisons with HD-IIV3.

Table 1. Adjusted relative vaccine effectiveness (rVE) of aIIV3 versus comparators in high-risk patients in the 2017–2018 and 2018–2019 influenza seasons in the U.S.

Conclusion

The results of this study support the use of aIIV3 in adults ≥65 years of age at high risk for influenza complications and provides further evidence supporting aIIV3 as an effective public health measure against influenza.

Disclosures

Lauren Fischer, M.A., Seqirus (Consultant) Dan O'Brien, BA, Seqirus (Consultant) Joseph Vasey, PhD, Seqirus (Consultant) Gregg C. Sylvester, MD, Seqirus (Employee) James A. Mansi, PhD, Seqirus (Employee)

2470. The Effect of Information–Motivation–Behavioral Skills Model-Based Continuing Medical Education on Pediatric Influenza Immunization Uptake: A Randomized, Controlled Trial

Background

Seasonal vaccination against influenza is the most important public health strategy to prevent influenza morbidity and mortality in children 6–23 months of age. However, influenza immunization uptake in this population remains sub-optimal. While parents look to healthcare professionals (HCPs) for guidance, HCPs may be neither aware of the burden of influenza disease in infants nor familiar with ways to address parental influenza vaccine hesitancy. The objective of this research was to describe the impact of an Information—Motivation—Behavioral Skills model (IMB)-based, accredited, online Continuing Medical Education (CME) program on seasonal influenza vaccination in children 6–23 months of age in Ontario, Canada during the 2016/2017 influenza season.

Methods

A multi-center, randomized, controlled trial was conducted whereby HCPs were randomized to either an accredited IMB-based CME or to routine practice (no CME). The CME addressed influenza burden in young children and identified parental barriers (hesitancy) to influenza vaccination, designed to inform, motivate, and upskill HCPs. All vaccine options were reviewed, including the adjuvanted, trivalent, inactive, influenza vaccine (aTIV). Immunization rates were compared between groups using Pearson’s chi-squared and a logistic regression model adjusting for socioeconomic status at the clinic-level.

Results

A total of 68 HCPs were recruited: 33 randomized to the CME group and 35 to routine practice. HCP interactions with parents were evaluated during 628 visits: 292 visits by HCPs in the CME group and 336 by HCPs in the routine practice group. Parents seen by HCPs in the CME group were ~30% more likely to agree to immunize their child with seasonal influenza vaccination compared with parents seen by HCPs in the control group (P = 0.007). The adjusted odds of influenza immunization were 1.5 times higher in the CME group compared with the control group. Children in the CME group were ~20% more likely to receive aTIV compared with children in the control group (P < 0.001).

Conclusion

HCP education with a tailored health behavior uptake model based CME addressing the burden of influenza disease in young children and influenza vaccine hesitancy was associated with a significant increase in influenza immunization.

Disclosures

W. Fisher, Seqirus: Consultant and Investigator, Consulting fee and Speaker honorarium. J. Yaremko, Seqirus: Collaborator and Investigator, Speaker honorarium. V. Brown, Seqirus: Investigator, Speaker honorarium. H. Garfield, Seqirus: Investigator, Speaker honorarium. E. Rampakakis, Seqirus: Independent Contractor, Consulting fee. C. Boikos, Seqirus: Employee, Salary. J. A. Mansi, Seqirus: Employee and Shareholder, Salary.

Vaccination against herpes zoster in developed countries: state of the evidence

Although progress has been made in the treatment of herpes zoster (HZ) and postherpetic neuralgia (PHN), available therapeutic options are only partially effective. Given evidence that a live-attenuated varicella-zoster-virus vaccine is effective at reducing the incidence of HZ, PHN and the burden of illness, policymakers and clinicians are being asked to make recommendations regarding the use of the zoster vaccine. In this report, we summarize the evidence regarding the: (1) burden of illness; (2) vaccine efficacy and safety; and (3) cost-effectiveness of vaccination, to assist evidence-based policy making and guide clinicians in their recommendations. First, there is general agreement that the overall burden of illness associated with HZ and PHN is substantial. Second, the safety and efficacy of the zoster vaccine at reducing the burden of illness due to HZ and the incidence of PHN have been clearly demonstrated in large placebo-controlled trials. However, uncertainty remains about the vaccine's duration of protection. Third, vaccination against HZ is likely to be cost-effective when the vaccine is given at approximately 65 y of age, if vaccine duration is longer than 10 y.

Employment related productivity loss associated with herpes zoster and postherpetic neuralgia: a 6-month prospective study

We conducted a prospective multi-center study to assess productivity loss associated with herpes zoster (HZ) and postherpetic neuralgia (PHN). From 10/2005 to 07/2006, we recruited immunocompetent subjects aged ≥50 years with HZ within 14 days of rash onset across Canada. Of the 249 patients recruited, 88 were employed. Data on employment status, absences from work, reasons for absence and effectiveness at work were documented at recruitment, 7-14-21-30-60-90-120-150 and 180 days later. The majority (64%) of employed subjects missed work because of HZ and 76% reported decreased effectiveness at work (i.e. presenteeism) because of HZ/PHN. Mean hours of absenteeism and presenteeism per working individual were 27 and 34 h, respectively. Pain severity and duration were associated with greater productivity loss. These results provide new information about the burden of HZ and PHN, which is useful for public health planning and cost-effectiveness analyses of HZ vaccination among individuals of working age.

Predictors of postherpetic neuralgia among patients with herpes zoster: a prospective study

Postherpetic neuralgia (PHN) is the most common complication of herpes zoster (HZ). The main objectives of this study were to: 1) estimate the severity and duration of PHN; and 2) identify the predictors of PHN. From October, 2005 to July, 2006, 261 outpatients with HZ, aged ≥ 50, were recruited within 14 days of rash onset during the routine clinical practice of 83 physicians across Canada. Physicians documented HZ characteristics, treatments, general health, functional, and immune status. HZ pain was measured at recruitment and on days 7, 14, 21, 30, 60, 90, 120, 150, and 180 following recruitment. PHN was defined as a worst pain ≥ 3 persisting or appearing more than 90 days after rash onset. Predictors of PHN were obtained by hierarchical log-binomial regression. Twenty-two percent of 249 immunocompetent subjects with HZ developed PHN. Median duration of PHN was 77 days. Independent predictors of PHN included: older age, limitation in performing usual activities prior to HZ, and pain severity at recruitment. This study confirms that older age and greater acute pain severity are predictors of PHN, while functional status emerges as a novel independent predictor of PHN that deserves further exploration. These findings will contribute to optimal use of the HZ vaccine and testing of new therapies that might prevent PHN.

PERSPECTIVE

This study confirmed that older age and greater acute pain severity are robust predictors of PHN, whereas functional status emerged as a novel predictor. Despite the high proportion of subjects treated with antivirals, the burden of PHN remains considerable, suggesting that prevention and additional early interventions are needed to reduce the burden of HZ.

The impact of herpes zoster and postherpetic neuralgia on health-related quality of life: a prospective study

BACKGROUND

Vaccination against herpes zoster is being considered in many countries. We conducted a multicentre prospective study to describe the impact of herpes zoster and postherpetic neuralgia on health-related quality of life.

METHODS

From October 2005 to July 2006, 261 outpatients aged 50 years or older with herpes zoster were recruited from the clinical practices of 83 physicians within 14 days after rash onset. The Zoster Brief Pain Inventory was used to measure severity of pain and interference with activities of daily living because of pain. The EuroQol EQ-5D assessment tool was used to measure quality of life. These outcomes were assessed at recruitment and on days 7, 14, 21, 30, 60, 90, 120, 150 and 180 following recruitment.

RESULTS

Acute herpes zoster interfered in all health domains, especially sleep (64% of participants), enjoyment of life (58%) and general activities (53%). The median duration of pain was 32.5 days. The median duration of interference with activities of daily living because of pain varied between 27 and 30 days. Overall, 24% of the participants had postherpetic neuralgia (pain for more than 90 days after rash onset). Anxiety and depression, enjoyment of life, mood and sleep were most frequently affected during the postherpetic neuralgia period. The mean EQ-5D score was 0.59 at enrolment and remained at 0.67 at all follow-up points among participants who reported clinically significant pain.

INTERPRETATION

These data support the need for preventive strategies and additional early intervention to reduce the burden of herpes zoster and postherpetic neuralgia.

Effect of stress exposure on the activation pattern of enkephalin-containing perikarya in the rat ventral medulla

We examined the effects of acute and chronic psychogenic stress on the activation pattern of enkephalin-containing perikarya in the rat ventrolateral medulla. Rats allocated to the chronic stress groups were subjected to 90 min of immobilization for 10 days. On the 11th day, the chronically stressed rats were exposed to homotypic (90-min immobilization) or to heterotypic but still psychogenic (90-min immobilization coupled to air jet stress) stress. The acute stress group was subjected once to an acute 90-min immobilization. For each group, the rats were anesthetized either before stress (time 0) or 90, 180, and 270 min after the onset of stress. Brain sections were then processed using immunocytochemistry (Fos protein) followed by radioactive in situ hybridization histochemistry (enkephalin mRNA). Following immobilization, the acute group displayed a marked increase in the number of activated enkephalin-containing perikarya within the paragigantocellularis and lateral reticular nuclei. This level of activation was sustained up to 180 min following the onset of the immobilization stress and had returned to baseline levels by 270 min from the initiation of the stress. However, this stress-induced activation of enkephalin-containing perikarya of the ventrolateral medulla was not seen following either homotypic or heterotypic stress in the chronically stressed group. These results provide evidence that enkephalin-containing perikarya of the ventrolateral medulla may constitute a potential circuit through which they regulate some aspect of the stress responses. Conversely, this enkephalinergic influence from the ventrolateral medulla was shown to be absent following chronic stress exposure. This would suggest a decrease in enkephalin inhibitory input originating from the ventrolateral medulla, thereby allowing a neuroendocrine and/or autonomic response to chronic stress.

Effect of immobilization stress on transcriptional activity of inducible immediate-early genes, corticotropin-releasing factor, its type 1 receptor, and enkephalin in the hypothalamus of borderline hypertensive rats

The effects of immobilization on the expression of immediate-early gene c-fos and nerve growth factor-inducible (NGFI)-B mRNAs, corticotropin-releasing factor (CRF) mRNA, CRF heteronuclear RNA (hnRNA), CRF receptor types 1 and 2alpha mRNA, and enkephalin hn/mRNA were investigated in the hypothalamic paraventricular nucleus of Wistar-Kyoto (WKY) rats and borderline hypertensive rats (BHRs). Rats were deeply anesthetized 0, 30, 60, and 180 min after the beginning of the immobilization session (60 min maximum). BHR paraventricular nuclei displayed slight differences in their resting levels of NGFI-B mRNA and CRF hnRNA, both being significantly elevated compared with those of WKY rats. Conversely, basal levels of enkephalin primary transcript were significantly lower in BHRs. Immobilization, however, induced transient variations in the hybridization signals for all evaluated genes within the paraventricular nucleus (except for CRF 2alpha receptor). Immediate-early gene mRNA levels were higher and more prolonged in BHRs than in WKY rats. This heightened neuronal activation in the BHRs was associated with a more rapid increase in CRF mRNA expression (30 min) compared with that in WKY rats (60 min). It is interesting that a transient rise in CRF hnRNA levels was detected in stressed WKY rats, whereas the BHR group displayed a progressive decline in this transcript, being significantly below resting levels 180 min after the immobilization session. The stress-induced expression of CRF type 1 receptor mRNA was similar in both strains. Moreover, no significant differences were observed for enkephalin hn/mRNA in either strain during the immobilization session. Therefore, the hypothalamic paraventricular nucleus appears to be involved in the functional hyperreactivity of the hypothalamic-pituitary-adrenal and autonomic axes to stress observed in BHRs, which may lead ultimately to a stress-induced hypertensive state.

Chronic stress induces sensitization in sympathoadrenal responses to stress in borderline hypertensive rats

The effects of acute foot shock on cardiovascular and sympathoadrenal responses were investigated in chronically stressed borderline hypertensive rats (BHR) and Wistar-Kyoto (WKY) rats. Male BHRs were divided into two groups; the maturation group (Mat) was not stressed, whereas the chronic stress group (AJS) received 8 wk (5 days/wk, 30 min/day) of air-jet stress coupled with immobilization. After chronic stress, the rats were cannulated in the femoral artery and jugular vein. Resting mean arterial pressure (MAP), heart rate (HR), and plasma norepinephrine (NE) levels were higher in the AJS group. In contrast, chronic stress failed to increase basal arterial pressure or HR in WKY rats. In response to acute foot shock, the Mat group had higher MAP increases, at which they plateaued, whereas the AJS rats displayed a progressive decline in MAP. This was associated with higher plasma NE and epinephrine levels but a smaller increase in adrenocorticotropic hormone in AJS versus Mat rats. This hyperactivity in the sympathoadrenal system of chronically stressed BHRs may, in part, account for their mild hypertension.

Regulation of corticotropin-releasing factor type 1 (CRF1) receptor messenger ribonucleic acid in the paraventricular nucleus of rat hypothalamus by exogenous CRF

The present study sought to examine the effects of intracerebroventricular (icv) administration of corticotropin-releasing factor (CRF) on the expression of CRF1 receptor messenger RNA (mRNA) within the hypothalamus as determined by quantitative in situ hybridization histochemistry. Adult male Sprague-Dawley rats were stereotaxically implanted with guide cannulae directed towards the right lateral ventricle. After 8-10 days of recovery, either 10 microliters CRF (5 micrograms) or vehicle solution was injected into the lateral ventricle over a 2-min period. The rats were then deeply anesthetized at 15, 60, and 180 min after icv injection, transcardially perfused, and their brains cut into 30-micron coronal sections. Brain sections were then processed using standard radioactive in situ hybridization histochemistry revealing the expression of the CRF1 receptor mRNA. Low to moderate basal levels of CRF1 receptor transcript were observed in several regions of the forebrain. However, the hybridization signal for the mRNA encoding the CRF1 receptor was barely detectable in the paraventricular nucleus of the hypothalamus (PVN) of vehicle-injected rats. In contrast, 180 min after icv administration of CRF, a significant increase in CRF1 receptor transcript was measured specifically in the PVN, despite having virtually any hybridization signal before 180 min. This increase in the level of receptor transcription by CRF was restricted to the type 1 receptor subtype because the hybridization signal for the CRF2 alpha receptor mRNA was unaffected in the brain regions in which it was located. Moreover, we confirmed previous findings of a CRF-induced neuronal activation of parvocellular neurosecretory cells of the PVN, as assessed by c-fos mRNA expression. This neuronal activation induced by exogenous CRF was also associated with a rapid and strong induction of CRF heteronuclear RNA selectively in the rat PVN, a phenomenon abolished by a pretreatment with a CRF receptor antagonist. These results provide evidence that elevated levels of central CRF may trigger CRF1 receptor transcription selectively in the PVN. This positive feedback of CRF on its own receptor may represent a functional adaptation of the hypothalamic-pituitary-adrenal axis in response to stress.

Cardiodynamic responses during seated and supine recovery from supramaximal exercise

The cardiodynamic responses of 9 healthy men (mean age +/- SD, 22.3 +/- 2.0 yrs) were measured during seated and supine passive recovery following the Wingate Anaerobic Power Test (WAPT). Stroke index (SI) was determined noninvasively using impedance cardiographic techniques. During the initial stages of seated recovery, SI progressively increased (1 min, 60.4 +/- 6.6 ml/m2; 3 min, 64.6 +/- 5.9 ml/m2) and achieved peak levels by 5 min (70.5 +/- 6.2 ml/m2). Between Minutes 3 and 10 of seated recovery, SI was significantly (p < or = 0.05) higher than the preexercise value (46.0 +/- 4.0 ml/m2). A similar response pattern for SI was observed during supine recovery. The systemic vascular resistance index (SVRI) decreased by 101% and 114% from preexercise baseline values after 1 min of recovery in the supine and seated postures, respectively. The persistent rise in SI during the first 10 min of passive seated recovery may be explained by the sustained attenuation in SVRI coupled with the anticipated residual myocardial inotropic effects following the WAPT.