A Prospective Cohort Study on Pregnancy Outcomes of Persons Immunized with a Seasonal Quadrivalent Inactivated Influenza Vaccine during Pregnancy

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.

Repeated exposure to an MF-59 adjuvanted quadrivalent subunit influenza vaccine (aQIV) in children: Results of two revaccination studies

BACKGROUND

Pediatric adjuvanted seasonal influenza vaccines induce higher immune responses and have the potential to confer better protection against influenza among young vaccine-naïve children. Limited data describe benefits and risks of repeated administration of adjuvanted influenza vaccines in children. Two revaccination studies assess the safety and immunogenicity of repeated exposure to an MF59-adjuvanted quadrivalent influenza vaccine (aQIV; Fluad®) compared to routine non-adjuvanted quadrivalent influenza vaccine (QIV).

METHODS

Children previously enrolled in the parent study, who received vaccination with aQIV or nonadjuvanted influenza vaccine (TIV or QIV), were recruited in Season 1 (n = 607) or Season 2 (n = 1601) of the extension trials. Season 1 participants remained in their original randomization groups (aQIV-aQIV or TIV-QIV); Season 2 subjects were re-randomized to either vaccine, resulting in four groups (aQIV-aQIV, aQIV-QIV, QIV-aQIV, or QIV-QIV). All subjects received a single-dose vaccination. Blood samples were taken for immunogenicity assessment prior to vaccination and 21 and 180 days after vaccination. Reactogenicity (Days 1-7) and safety were assessed in all subjects.

RESULTS

Hemagglutination inhibition (HI) geometric mean titer (GMT) ratios demonstrated superiority of aQIV revaccination over QIV revaccination for all strains in Season 1 and for A/H1N1, B/Yamagata, and B/Victoria in Season 2. Higher HI titers against heterologous influenza strains were observed after aQIV vaccination during both seasons. Mild to moderate severity and short duration reactogenicity was more common in the aQIV than QIV groups, but the overall safety profiles were similar to the parent study.

CONCLUSION

The safety and immunogenicity results from this study demonstrate benefit of aQIV for both priming and revaccination of children aged 12 months to 7 years.