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Immune response to split-product influenza vaccine in preterm and full-term young children
J R Groothuis1, M J Levin, M V Lehr
1Department of Pediatrics, University of Colorado School of Medicine, Denver.
Insights
Influenza vaccination in children shows that while split-product vaccines are immunogenic, prematurity and health status impact immune responses. Full-term infants generally exhibit stronger cellular immunity to influenza antigens.
Area of Science:
- Pediatrics
- Immunology
- Vaccinology
Background:
- Influenza poses a significant health risk to young children, particularly those with underlying conditions like bronchopulmonary dysplasia.
- Assessing the immunogenicity of influenza vaccines in diverse pediatric populations is crucial for public health strategies.
Purpose of the Study:
- To evaluate humoral and cellular immune responses to a two-dose influenza split-product vaccine in children aged 6-48 months.
- To compare immune responses between healthy full-term infants, sick preterm infants with bronchopulmonary dysplasia, and reimmunized ex-preterm children.
Main Methods:
- Humoral immunity assessed via haemagglutination inhibition (HI) and ELISA.
- Cellular immunity measured by enumerating memory T cells.
- Participants included previously unimmunized full-term infants, sick preterm infants, and reimmunized ex-preterm children (active or recovered bronchopulmonary dysplasia).
Main Results:
- ELISA antibody levels were significantly higher in unimmunized full-term infants compared to unimmunized sick preterm infants.
- Over 90% of children achieved protective HI titres (≥1:32), maintained for at least 20 weeks.
- T-cell responses to influenza antigen were significantly greater in full-term children than preterm children, irrespective of health status or prior immunization.
Conclusions:
- Split-product influenza vaccine is immunogenic across various pediatric cohorts.
- Preterm birth, health status, and prior immunization history significantly influence the magnitude of immune responses to influenza vaccination.
- Full-term infants demonstrate more robust T-cell mediated immunity to influenza antigens.
Abstract:
Humoral and cellular immune responses to two doses of influenza antigens were measured in children 6-48 months of age. These vaccinees comprised a previously unimmunized cohort of 18 healthy full-term children and 15 sick preterm children with bronchopulmonary dysplasia and an additional 30 ex-preterm children who were reimmunized. Half of the reimmunized cohort were recovered from bronchopulmonary dysplasia and half had active bronchopulmonary dysplasia. Antibody response was measured by haemagglutination inhibition (HI) and ELISA, and cellular immunity was measured by enumerating memory T cells. Six weeks after immunization, ELISA antibody levels were significantly higher in previously unimmunized full-term vaccinees than in previously unimmunized sick preterm infants (p less than 0.002). No difference was found between sick and recovered reimmunized children. By HI testing greater than 90% of children in both cohorts developed titres greater than or equal to 1:32, and these were generally maintained for at least 20 weeks. T-cell proliferative responses to influenza antigen were greater in the full-term children than in the preterm children (p less than 0.02), irrespective of state of health or prior immunization status. Split-product vaccine was immunogenic in all the cohorts studied; however, factors such as prematurity, health status and previous influenza immunization played important roles in the magnitude of some responses.