High prevalence of IgE sensitization to inactivated influenza vaccines,
yet robust IgG4 responses, in a healthy pediatric population
Abstract
Background: Anaphylaxis following influenza vaccination is a rare but
serious problem. The underlying immune responses are not well
understood. This study elucidated the IgE and IgG antibody responses in
healthy children and adolescents following inactivated influenza
vaccines (IIVs). Methods: The efficacy and safety of quadrivalent IIV
(QIV) and trivalent IIV (TIV) were compared in healthy subjects aged
0-18 years. Serum IIV-specific IgE, IgG and IgG4 levels (sIgE, sIgG,
sIgG4) were measured with ImmunoCAP. Hemagglutinin inhibition (HI) assay
was performed for each influenza virus subtype. Sera from earlier
patients who developed anaphylaxis to different IIVs were similarly
tested. Results: A total of 393 subjects were enrolled: 96 were 6 months
-2 years old, 100 were 3-5 years old, 100 were 6-12 years old, and 97
were 13-18 years old. No anaphylaxis was observed. Generally, QIV and
TIV induced similar antibody responses. IIV-sIgE levels rose
significantly after vaccination in the 6m-2y and 3-5y groups, did not
change in the 6-12y group, and decreased in the 13-18y group. In
contrast, the IIV-sIgG4/sIgE ratio increased significantly after
vaccination in all age groups. Sensitized subjects had significantly
higher HI titers and IIV-sIgG levels in the youngest age group and
higher IIV-sIgG4 levels in all age groups compared with the
non-sensitized. The IIV-sIgG4/sIgE ratio in 5 patients with anaphylaxis
was significantly lower than in age-matched healthy subjects.
Conclusion: IIVs induce IgE sensitization in healthy children, but also
robust IgG4 responses that may protect them from anaphylaxis.