Safety of recombinant quadrivalent influenza vaccine compared to inactivated influenza vaccine in Chinese adults: An observational study.

BACKGROUND:Recombinant influenza vaccine (RIV) has been in use in US adults since 2013. This study evaluated the safety of quadrivalent recombinant influenza vaccine (RIV4, Flublok® Quadrivalent, Sanofi Pasteur) compared with standard-dose quadrivalent inactivated influenza vaccine (SD-IIV4) in self-identified Chinese adults at Kaiser Permanente Northern California (KPNC). METHODS:This study evaluated adults aged 18-64 years within KPNC during the 2018-2019 influenza season who self-identified as Chinese (NCT03694392). We compared the rates of prespecified diagnoses of interest in the emergency department and inpatient settings as done in prior influenza studies, for three risk intervals: 0-2 days, 0-13 days, and 0-41 days following influenza vaccination, as well as number of deaths within 0-180 days after vaccination. We estimated the odds ratios (ORs) and 95% confidence intervals using logistic regression adjusted for sex, age group, presence of comorbidities, and same-day concomitant vaccination. RESULTS:Comparing 15,574 adults who received RIV4 with 27,110 who received SD-IIV4, there was no statistically significant difference in the prespecified diagnoses of interest and deaths between the 2 groups. There were 35 deaths total, none of which were considered to be related to influenza vaccination. CONCLUSIONS:This study did not identify any safety concerns regarding RIV4 use among 18-64-year-olds who self-identified as Chinese. This study supports the safety of RIV4 vaccine in this population.