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Background: Invasive Haemophilus influenzae type b (Hib) infection has a high morbidity among young children, but the burden of disease and rate of Hib are different in different regions. The aim of the present study was to investigate the levels of Hib antibodies and the oropharyngeal Hib prevalence in young children. Methods: One hundred-fifty nine healthy children aged 19–36 months of age were included in this cross-sectional study. Anti-polyribosylribitol phosphate (anti-PRP) antibody concentrations were measured using commercially available enzyme-linked immunosorbent assay (ELISA), and serotyping of isolated Hib strains was conducted by slide agglutination with specific antisera. Results: Of the study participants, 57 (35.8%) were fully vaccinated (group 1A); 17 (10.7%) were incompletely vaccinated (group 1B), and 85 (53.5%) were non-vaccinated (group 2). Geometric mean titer (GMT) of anti-PRP antibody was 3.8 μg/mL, 2.2 μg/mL and 0.49 μg/mL in group 1A, group 1B and group 2, respectively. While all children in group 1 (n = 74) had seroprotective antibody concentrations (≥0.15 μg /mL), of the children in group 2 (n = 85) 31.8% did not have seroprotective anti-PRP levels (P

The neonatal immune system is immature and may be affected by Bacillus Calmette-Guerin (BCG) vaccine. We investigated the influence of BCG given at two different ages on the peripheral blood (PB) T-cell subpopulations. Forty full term healthy newborns were randomly chosen. Twenty of them were vaccinated with BCG at birth (group I) and the remaining at the age of 2 months (group II). The cell analysis were carried out before (pre-BCGI and pre-BCGII), and 2 months after (post-BCGI and post-BCGII) the vaccination. The analysis of the gamma/delta and alpha/beta T-cell receptor (TCR) antigens was done by two-colour flowcytometer. The purified protein derivative (PPD) response was investigated 2 months after vaccination. The results showed that although T-cell (TCR+ cell) counts showed no difference in PB before and after vaccination in both study groups, the total lymphocyte and non-T cell (TCR- cell) populations increased significantly whereas alphabetaT-cell population significantly decreased after vaccination. On the contrary, gammadeltaT-cell counts in PB increased significantly 2 months after vaccination in group I but not in group II. Total lymphocyte and non-T cell counts in vaccinated infants at 2 months of age (post-BCGI) were significantly higher than in unvaccinated infants of the same age whereas alphabetaT-cell count in vaccinated infants was significantly low. However, total T-cell and gammadeltaT-cell counts showed no difference. PPD positivity was similar in both study groups (61% in group I, 66% in group II). Neither alphabetaT- nor gammadeltaT-cell counts were different in PPD positive and PPD negative infants. Our study shows that BCG causes marked quantitative changes in the PB T-cell subpopulations in young infants.