Janine Oberye

Background: Children are at high risk of influenza infections and may spread the disease to vulnerable family members. Quadrivalent influenza vaccines (QIV) provide protection against four strains of influenza recommended annually by the World Health Organization (WHO) and have the potential to provide improved protection during seasons with B-strain mismatch between vaccine and circulating virus strains. Methods: We evaluated the reactogenicity and safety of a QIV (Afluria Quad and Afluria Quad Junior, Seqirus, Parkville, Australia) in children aged 6 months to <3 years and 3 to <9 years over two Southern Hemisphere influenza seasons (2019 and 2020). The rates of solicited local and systemic adverse events (AEs) occurring on Days 1–7 after each vaccine dose were compared between three vaccine batches during each of the two seasons. Results: Overall, 73.7% of participants aged 6 months to <3 years and 77.5% of those aged 3 to <9 years reported any solicited AE between Day 1 and 7 of SH2019, and 66.7% and 69.2%, respectively, reported any solicited AE in SH2020, consistent with results from prior paediatric studies of QIV. The majority of solicited AEs were mild to moderate in severity. No consistent patterns of batch variation in solicited local or systemic reactogenicity were observed, suggesting no clinically significant differences between vaccine batches. No serious AEs or AEs of special interest (i.e., anaphylactic reaction or febrile convulsion) were reported during Days 1–7 after each vaccination, and no new safety concerns were identified. Conclusions: Together, these results support a clinically acceptable safety and tolerability profile of QIV in children aged 6 months to <9 years.

Adults aged 50–64 years have a high incidence of symptomatic influenza associated with substantial disease and economic burden each year. We conducted a randomized, controlled trial to compare the immunogenicity and safety of an adjuvanted quadrivalent inactivated influenza vaccine (aIIV4; n = 1027) with a nonadjuvanted standard dose IIV4 (n = 1017) in this population. Immunogenicity was evaluated on Days 22, 181, and 271. On Day 22, upper limits (UL) of 95% confidence intervals (CI) for geometric mean titer (GMT) ratios (IIV4/aIIV4) were <1.5 and 95% CI ULs for the difference in seroconversion rate (SCR IIV4 − aIIV4) were <10% for all four vaccine strains, meeting primary endpoint noninferiority criteria. Protocol-defined superiority criteria (95% CI ULs < 1.0) were also met for A(H1N1) and A(H3N2). Immune responses following aIIV4 vaccination were more pronounced in persons with medical comorbidities and those not recently vaccinated against influenza. Safety data were consistent with previous studies of MF59 adjuvanted seasonal and pandemic influenza vaccines. These findings support the immunological benefit of aIIV4 for persons aged 50–64 years, especially those with comorbidities.

This US-based, prospective observational cohort study evaluated the safety of a quadrivalent inactivated influenza vaccine (IIV4; Afluria Quadrivalent) in pregnant persons immunized over four influenza seasons between 2017 and 2021. Pregnancy outcomes included live birth, stillbirth, spontaneous abortion, and elective termination. Infant events of interest were major congenital malformations (MCMs), preterm birth (<37 weeks gestational age), and low birth weight (LBW). Data were descriptive; prevalence point estimates were reported with 95% confidence intervals (CI). A total of 483 pregnant persons were given IIV4 and evaluated; 477 (98.8%) reported a live birth, and there were 2 stillbirths, 4 spontaneous abortions, and no elective terminations or maternal deaths. The prevalence rates of infant events were as follows: preterm birth, 7.2% (upper 95% CI, 9.6%); LBW, 5.4% (upper 95% CI, 7.4%); and MCMs, 0.8% (upper 95% CI, 1.9%). Point estimates and upper 95% CIs of the observed prevalence rates were lower than or similar to background prevalence in the general US population. Our findings suggest no evidence of a safety concern with vaccinating this group at high risk of influenza complications and are consistent with published data from databases and surveillance systems that monitor the safety of influenza vaccines in pregnant persons.