Dataset Information

2322. Effectiveness of Recombinant Influenza Vaccine vs. Standard Dose Inactivated Influenza Vaccines Against Hospitalized Influenza-Related Outcomes in Adults: A Cluster Randomized Trial

ABSTRACT: Abstract

Background

More effective influenza vaccines are needed to prevent influenza and its complications. Recombinant influenza vaccines may offer better protection than traditional egg-based vaccines. Using a cluster randomized design to estimate the relative vaccine effectiveness (rVE) of Flublok Quadrivalent recombinant influenza vaccine (RIV4) vs. standard dose inactivated influenza vaccine (SD-IIV4), we separately reported that RIV4 provided significantly better protection against primary outcome of confirmed influenza in adults 50–64 yrs in the 2018–20 moderately severe influenza seasons. Here we report the rVE against the secondary and exploratory outcomes of hospitalized influenza-related outcomes.

Methods

We randomized 66 facilities within Kaiser Permanente Northern California (KPNC) to routinely administer RIV4 or SD-IIV4 to adults, alternating vaccine formulations weekly by facility during the influenza season (ClinicalTrials.gov NCT03694392). Hospitalized cases of PCR-confirmed influenza, community-acquired pneumonia, and cardio-respiratory events were prespecified as secondary in 50–64 yrs and exploratory in 18–49 yrs. We estimated the relative hazard ratio (rHR) using Cox regression on a calendar timeline, adjusting for age, sex, and race, using facility-specific stabilized propensity scores. We calculated rVE as (1–rHR) x 100%.

Results

During the 2018–19 and 2019–20 seasons, the study consisted of 1,630,328 vaccinees 18–64 yrs (RIV4=632,962; SD-IIV4=997,366), and included 95 hospitalized influenza cases after RIV4 and 153 after SD-IIV4 among 50–64 yrs (Table 1). RIV4 vs. SD-IIV4 was not significantly more protective against hospitalized influenza-related outcomes in adults 50–64 yrs or 18–49 yrs.

Conclusion

While this large cluster randomized study found that RIV4 vs. SD-IIV4 reduced the risk of lab-confirmed influenza in adults 50–64 yrs across 2 influenza seasons, RIV4 and SD-IIV4 performed similarly against hospitalized influenza-related outcomes. Evaluating influenza-related hospitalizations during influenza seasons when more hospital outcomes occur may help to better understand the relative effectiveness of recombinant versus standard inactivated influenza vaccines against severe disease.

Disclosures

All Authors: No reported disclosures.

SUBMITTER:

PROVIDER: S-EPMC9752875 | biostudies-literature | 2022 Dec

REPOSITORIES: biostudies-literature

ACCESS DATA

Similar Datasets

Project description:BackgroundNew influenza vaccine formulations are designed to improve vaccine effectiveness and protect those most vulnerable to infection. High dose trivalent inactivated influenza vaccine (HD-IIV3), licensed for ages ≥65 years, produces greater antibody responses and efficacy in clinical trials, but post-licensure vaccine effectiveness (VE) compared to standard dose (SD-IIV3/4) vaccine remains an open question.MethodsUsing a test-negative, case control design and propensity analyses to adjust for confounding, US Influenza VE Network data from the 2015-2016 through 2018-2019 seasons were analyzed to determine relative VE (rVE) between HD-IIV3 and SD-IIV3/4 among outpatients ≥65 years old presenting with acute respiratory illness. Influenza vaccination status was derived from electronic medical records and immunization registries.ResultsAmong 3861 enrollees, 2993 (78%) were vaccinated; 1573 (53%) received HD-IIV3 and 1420 (47%) received SD-IIV3/4. HD-IIV3 recipients differed from SD-IIV3/4 recipients by race, previous vaccination, number of outpatient visits in the previous year and timing of vaccination, and were balanced in the propensity model except the timing of vaccination. Compared with no vaccination, significant protection against any influenza A was observed from both HD-IIV3 (VE = 29%; 95%CI = 10%, 44%) and SD-IIV3/4 (VE = 24%; 95%CI = 5%, 39%); rVE = 18% (95%CI = 0%, 33%, SD as referent). When stratified by virus type, against A/H1N1, HD-IIV3 VE was 30% (95%CI = -7%, 54%), SD-IIV3/4 VE was 40% (95%CI = 10%, 61%), and rVE = -32%; (95%CI = -94%, 11%); Against A/H3N2, HD-IIV3 VE was 31% (95%CI = 9%, 47%), SD-IIV3/4 VE was 19% (95%CI = -5%, 37%), and rVE = 27%; (95% CI = 9%, 42%).ConclusionsAmong adults ≥65 years of age, recipients of standard and high dose influenza vaccines differed significantly in their characteristics. After adjusting for these differences, high dose vaccine offered more protection against A/H3N2 and borderline significant protection against all influenza A requiring outpatient care during the 2015-2018 influenza seasons.