Post-licensure surveillance of quadrivalent inactivated influenza (IIV4) vaccine in the United States, Vaccine Adverse Event Reporting System (VAERS), July 1, 2013−May 31, 2015

BACKGROUND: Quadrivalent inactivated influenza vaccines (IIV4) were first available for use during 2013−14 influenza season for individuals aged ≥6 months. IIV4 is designed to protect against four different flu viruses; two influenza A viruses and two influenza B viruses. METHODS: We searched the Vaccine Adverse Event Reporting System (VAERS) for US reports after IIV4 and trivalent inactivated influenza vaccine (IIV3) from 7/1/2013–5/31/2015. Medical records were requested for non-manufacturer reports classified as serious (i.e. death, hospitalization, prolonged hospitalization, life-threatening illness, permanent disability). The review included automated data analysis, clinical review of all serious reports, reports of special interest, and empirical Bayesian data mining. RESULTS: VAERS received 1,838 IIV4 reports; 512 (28%) in persons aged 6 months–17 years of which 42 (8.2%) were serious reports; 1,265 (69%) in persons aged >18 years of which 84 (6.6%) were serious reports; two in children <6 months and 59 in persons of unknown age. Injection site erythema (24%), fever (14%) and injection site swelling (17%) were the most frequent adverse events among persons aged 6 months–17 years, while injection site pain (16%), pain (15%) and pain in extremity (13%) were the most frequent among persons aged 18−64 years given the vaccine alone. Among non-death serious reports, injection site reactions, constitutional symptoms, Guillain-Barré syndrome, seizures, and anaphylaxis were the most frequently reported adverse events. Data mining detected disproportional reporting for incorrect vaccine administration with no associated adverse events. Adverse events following IIV4 reported to VAERS were similar to those following IIV3. CONCLUSIONS: In our review of VAERS reports, IIV4 had a similar safety profile to IIV3. Most of the reported AEs were non-serious. Our findings are consistent with data from pre-licensure studies of IIV4.