996. A Cluster-Randomized Trial of Adjuvanted Trivalent Influenza Vaccine vs. Standard Dose in US Nursing Homes
Authors: Gravenstein Stefan , Davidson H Edward , Mcconeghy Kevin , Han Lisa , Canaday David , Saade Elie , Baier Rosa R , Mor Vincent 
Published: November 2018

Abstract

Background
Pneumonia and influenza lead as vaccine-preventable infections among nursing home (NH) residents. Immunosenescence reduces vaccine response and protection from infections. More immunogenic vaccines, e.g., adjuvanted trivalent influenza vaccine [aTIV], can improve clinical outcomes. We evaluated all-cause hospitalization among long-stay NH residents offered aTIV vs. trivalent influenza vaccine (TIV).

Methods
We randomized 823 NHs within 75 miles of a Centers for Disease Control and Prevention influenza reporting city to offer one of the two egg-based influenza vaccines, aTIV or TIV, as their 2016–2017 influenza season standard of care. For the subset of long-stay NH residents (&gt;100 days in facility as of October 1, 2016) aged ≥65 years, we determined how many were hospitalized from November 1, 2016 to June 1, 2017 on an intent-to-treat basis. We obtained all-cause hospitalization, patient-, and facility-level characteristics from Minimum Data Set and Certification and Survey Provider Enhanced Reporting data. Our primary outcome was time to first hospitalization, using Cox proportional hazards models.

Results
The analytic sample included 26,300 residents in 412 NHs randomized to offer aTIV and 26,474 in 410 NHs randomized to TIV. Mean age was 82.3 vs. 82.3 years, 69.3% vs. 68.6% were women, and 15.5% vs. 20.1% were African-American, for aTIV and TIV NHs, respectively. The number of residents vaccinated in the facility against influenza was 17,976 (68.3%) and 18,364 (69.4%), with an overall vaccination rate of 78.4% and 79% for aTIV and TIV NHs. Mean staff vaccination was 53.4% and 54.4% for aTIV and TIV NHs. There were 5,479 (20.8%) hospitalizations in the aTIV and 5,839 (22.1%) in TIV NHs, respectively [adjusted as prespecified, hazard ratio (HR) 0.94, 95% confidence interval (CI): 0.88, 0.99]. Post-hoc adjustment for the imbalance in race increased heterogeneity, HR 0.97, 95% CI: 0.91, 1.04. A total of 18.2% vs. 17.5% (HR 1.05, 95% CI: 0.99, 1.11) of residents in aTIV and TIV NHs died.

Conclusion
Compared with TIV, aTIV may reduce hospitalization risk of long-stay NH residents during a predominantly A/H3N2 influenza season, despite reported reduced effectiveness due to egg-based mutagenesis of egg-based vaccines.
NCT: 02882100

Disclosures
S. Gravenstein, Seqirus: Consultant, Grant Investigator and Scientific Advisor, Consulting fee, Research grant and Speaker honorarium. H. E. Davidson, Seqirus: Grant Investigator and Investigator, Research grant and Research support. K. Mcconeghy, Seqirus: Investigator, Research support. L. Han, Seqirus: Investigator and Research Contractor, Research grant. D. Canaday, Seqirus: Grant Investigator, Research grant and Research support. E. Saade, Seqirus: Investigator, Research grant and Research support. R. R. Baier, Seqirus: Investigator, Research support. V. Mor, Seqirus: Investigator, Research grant and Research support.