Safety of Recombinant Influenza Vaccine Compared to Inactivated Influenza Vaccine in Adults: An Observational Study

BACKGROUND: Recombinant trivalent influenza vaccine (RIV3) was initially licensed in 2013 and approved for all adults ≥18 in 2014. This study evaluated the safety of RIV3 compared with trivalent standard-dose, inactivated influenza vaccine (IIV3) in Kaiser Permanente Northern California (KPNC). METHODS: This Phase 4 observational, postmarketing safety study included persons ≥18 years vaccinated with RIV3 or IIV3 in KPNC during the 2015–2016 influenza season. We compared (1) the rates of prespecified diagnoses of interest (Guillain-Barré Syndrome, pericarditis, pleural effusion, narcolepsy/cataplexy, asthma, acute hypersensitivity reactions, and fever) during various postvaccination risk intervals as well as (2) all-cause hospitalization and mortality 0–180 days after vaccination. We estimated odds ratios (ORs) and 95% confidence intervals (CIs) using logistic regression analyses adjusted for age, sex, race/ethnicity, month of vaccination, and concomitant receipt of other vaccinations. RESULTS: Comparing the 21 976 persons who received RIV3 with the 283 683 who received IIV3, there were statistically significant differences in the prespecified diagnoses of interest between the 2 groups. Specifically, RIV3 vaccination was associated with fewer fever diagnoses during the 0–41 days postvaccination (OR, 0.38; 95% CI, 0.14–0.86). Also, RIV3 was associated with fewer all-cause hospitalizations during the 0–180 days postvaccination (OR, 0.66; 95% CI, 0.61–0.73), which was mostly related to pregnancy-related hospitalizations in IIV3 recipients. There were no serious adverse events or deaths related to RIV3. CONCLUSIONS: This study did not identify any safety concerns regarding the use of RIV3 in adults.