Serological response to influenza vaccination among children vaccinated for multiple influenza seasons

Area of Science:

• Pediatric Infectious Diseases
• Immunology
• Vaccinology

Background:

• Influenza vaccination is crucial for child health.
• Understanding the impact of multiple seasonal vaccinations on immune response is important.
• Previous studies have not fully elucidated the long-term seroprotection effects in children.

Purpose of the Study:

• To evaluate if multiple seasons of influenza vaccination affect seroprotection proportions in children aged 3 to 15 years.
• To compare seroprotection rates against different influenza strains based on vaccination history.

Main Methods:

• A cohort of 131 healthy children (3-15 years) received trivalent inactivated influenza vaccine (TIV) for one, two, or three consecutive seasons (2005-2008).
• Antibody titers were measured using hemagglutination inhibition (HAI) assays against A/H1N1, A/H3N2, and B/Malaysia strains.
• Seroprotection proportions were analyzed using cut-points of 1:40 and 1:320, comparing outcomes based on the number of vaccination seasons.

Main Results:

• High seroprotection (>85%) was observed against A/H1N1 and A/H3N2 strains, irrespective of the number of TIV seasons or seroprotection cut-point used.
• For the B/Malaysia strain, seroprotection proportions did not change with the number of vaccination seasons.
• Lower seroprotection rates were noted for the B strain compared to A strains, and a higher cut-point (1:320) resulted in lower seroprotection than the 1:40 cut-point.

Conclusions:

• The proportion of children achieving seroprotection against influenza is not significantly affected by the number of vaccination seasons.
• While protection against influenza A strains remained high, the B strain showed lower and more variable seroprotection.
• These findings suggest that while annual vaccination is important, increasing the number of seasons vaccinated does not necessarily enhance seroprotection levels in children.