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. Objective: To elucidate 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. (239 words)