Evaluation of Waning Immunity at 6 Months after Both Trivalent and Quadrivalent Influenza Vaccination in Korean Children Aged 6–35 Months

Abstract

Background: The titer of influenza vaccine-induced antibodies declines over time, and younger children have lower immunogenicity and shorter duration of immunity. This study aimed to compare persistence of antibody at 6 months after influenza vaccination according to influenza virus strains, vaccine type, antigen dose, and primed status in children aged 6 to 35 months. Methods: A total 124 healthy children aged 6 to 35 months were enrolled from September to December 2016 at 10 hospitals in Korea and randomly assigned to either a full dose of quadrivalent influenza vaccine or a half dose of trivalent influenza vaccine with Victoria B strain group. Hemagglutination inhibition antibody titers (that measure the seroprotection rates) were assessed for the recommended influenza strains at 6 months post vaccination. Results: The seroprotection rates at 6 months for strains A (H1N1), A (H3N2), B/Yamagata, and B/Victoria were 88.7%, 97.4%, 36.6%, and 27.6%, respectively. The seroprotection rates for A (H1N1), A (H3N2) and B (Victoria) were 91.4%, 98.7% and 27.5% in a full dose of quadrivalent vaccine vs. 83.7%, 94.6% and 27.9% in a half dose trivalent vaccine, respectively. The seroprotection rate for the B (Yamagata) strain was 23.8% in the quadrivalent group and 14.0% in the trivalent group. Conclusion: Persistence of antibodies at 6 months was more favorable against the influenza A strains than against the B strains. Persistence of antibodies to additional B strain at 6 months was superior in the quadrivalent vaccine group. The immunity of primed children with different B strains was not superior to that of the unprimed group with another B strain.

Humoral Response to BNT162b2 Vaccine Against SARS-CoV-2 Variants Decays After Six Months

“…On the other hand, the decrease in antibody titers after vaccination is common for different vaccines. Some authors have reported a more significant decrease in antibodies against influenza B strains than A strains after six months of vaccination ( 28 ). Others have reported that antibody levels and avidity decrease between 8% and 23% after six months to 20 years of vaccination against measles, mumps, and rubella ( 29 ).…”

Optimal Time of Flu Shot: Influenza B Is the Problem

“…It is more complicated for children under 9 years of age who start their influenza vaccination for the first time, because they are even more vulnerable to the infection and need two shots over an at least 4 week interval 3. The article by Lee et al4 in this issue provides valuable evidence to relieve the concerns on the timing of vaccination against influenza A strains. The authors prospectively evaluated the persistence of immunity against influenza strains at 6 months after vaccination in young children and it was favorable against the influenza A strains.…”