Influenza-related hospitalizations in children younger than three years of age

[Vaccination schedule of the Spanish Association of Pediatrics: recommendations 2007]

The Vaccine Advisory Committee of the Spanish Association of Pediatrics provides information on the new developments in vaccines that have taken place in 2006 and recommends certain modifications to the Immunization Schedule for 2007. To ensure early protection, the measles-mumps-rubella (MMR) vaccine booster dose should be administered when children start school (3-4 years). Based on existing scientific evidence, the importance of universal heptavalent conjugate pneumococcal vaccination, as occurs in most similar European countries and in the autonomous community of Madrid in Spain, is confirmed. The safety and efficacy of rotavirus and human papilloma virus vaccines, as well as their use in our environment, is discussed and the role of pediatricians in their implementation is stressed. The recommended immunization schedule for children and adolescents starting vaccination late is also discussed.

[Recommendations of the Vaccine Advisory Committee of the Spanish Association of Pediatrics: influenza vaccination campaign 2006-2007]

The recommendations of the Spanish Association of Pediatrics on influenza vaccination in the pediatric age group for the 2006-2007 season are presented. Influenza has special characteristics in children due to the high morbidity it carries. Moreover, children constitute the most frequent source of transmission. The risk factors supporting influenza vaccination in children and the need for immunization in persons living with high-risk children are discussed. The advisability of extending vaccination in health workers, and specifically to pediatricians and medical personnel in contact with sick children is stressed. The composition of the vaccine for the 2006-2007 seasons, the schedules and dosages in children depending on age, and the contraindications to vaccination are specified. Finally, the premises required to recommend universal vaccination in young children in Spain as a strategy to reduce morbidity due to this epidemic in children and adults are discussed.

Humoral and cellular immune responses in children given annual immunization with trivalent inactivated influenza vaccine

BACKGROUND

There have been no prior reports of the frequency of circulating influenza-specific, interferon gamma-producing memory CD4+ and CD8+ T-cells in healthy children who have received multiple influenza immunizations.

METHODS

We evaluated 21 previously immunized children, ages 3 to 9 years, before and 1 month after administration of trivalent inactivated influenza vaccine. Frequencies of influenza-specific CD4+ and CD8+ T-cells stimulated with trivalent inactivated influenza vaccine or A/Panama (H3N2) virus were determined by flow cytometry, and antibody responses to vaccine strains and a drifted H3N2 strain were measured by hemagglutination inhibition assay and neutralizing antibody assays.

RESULTS

Mean change in CD4+ and in CD8+ T-cell frequencies after immunization was 0.01% (P > 0.39) with postimmunization CD4+ frequencies higher than CD8+ frequencies. Children with more previous vaccinations had a higher baseline frequency of CD4+ T-cells (P = 0.0002) but a smaller increase or even a decline from baseline after immunization (P = 0.003). An association between age and change in frequency was not detected. Baseline geometric mean titers (GMTs) and seroprotection rates were significantly higher in older children against A/Panama (neutralizing baseline GMT, P = 0.0488) and A/New Caledonia (hemagglutination inhibition baseline GMT and seroprotection, P < 0.0297). Baseline GMTs against B/Hong Kong were not associated with age or quantity of prior vaccinations.

CONCLUSIONS

These findings suggest that children may plateau in CD4+ T-cell responses to influenza antigens with repeated exposures and that the number of exposures may play a large role in building a memory CD4+ T-cell response to influenza A, perhaps independently from age.