On October 7, 2016, the Food and Drug Administration approved recombinant
hemagglutinin quadrivalent influenza vaccine (RIV4) (Spodoptera frugiperda cell line;
Flublok Quadrivalent) for active immunization for the prevention of
influenza disease in individuals 18 years of age and older. Clinical trials did not reveal any major differences in adverse events or serious adverse events following
Flublok Quadrivalent versus standard-dose quadrivalent inactivated
influenza vaccine. To improve our understanding of the safety profile of this
vaccine, we reviewed and summarized adverse event reports after
Flublok Quadrivalent administration to the
Vaccine Adverse Event Reporting System (VAERS). Through June 30, 2020, VAERS received 849 reports after RIV4 vaccination. The vast majority (810; 95%) were non-serious. Among serious events, there were 10 cases of
Guillain-Barré syndrome, including 5 people who required
mechanical ventilation and 2 people who died. Many
allergic reactions were reported as non-serious, but required interventions to treat a life-threatening event, e.g.,
epinephrine,
nebulizers,
albuterol,
glucocorticoids, and supplemental
oxygen. Two people experienced a positive rechallenge (i.e.,
allergic reactions after repeated vaccination with RIV4), including a person who-despite
premedication with
antihistamines-developed respiratory difficulties, required
epinephrine, and was transported to the emergency department. The occurrence of
anaphylaxis and other
allergic reactions in some individuals may reflect an underlying predisposition to atopy that may manifest itself after an exposure to any
drug or
vaccine, and does not necessarily suggest that
Flublok Quadrivalent is particularly allergenic. Postmarketing safety surveillance will continue to be vital for understanding the benefits and risks of quadrivalent recombinant
influenza vaccine.