Anticapsular Polysaccharide IgG Concentrations in Mexican Children Formerly Immunized with Haemophilus Influenzae b Prp-T Vaccine

Abstract

Background: In 1999 H. influenzae b (Hib) PRP-T vaccine was introduced into primary immunization schedule in Mexico. There have been no studies evaluating antibody response after widespread immunization in our country. It is now recognized that Hib conjugates induce significant initial antibody levels that in some cases wane over time. This study relies on the measurement of IgG serum antibody concentrations to Hib capsular polysaccharide (PS) and is interpreted in the light of the accepted levels ≥0.15 mg/mL for short-term protection against Hib invasive disease and ≥5.0 mg/mL for protection against Hib oropharyngeal carriage.Methods: Using a validated ELISA assay, we measured the IgG serum antibody concentrations in 115 children between 7 and 93 months of age who had received three doses of PRP-T. We used the standard reference serum US FDA 1983 for quantification of PS antibody levels. Concentrations were estimated using 3 rd degree polynomial regression lines. As there was no unvaccinated group available (>95% of Mexican children have received the Hib vaccine), the study was designed as a cross-sectional.Results: All children had serum IgG concentrations ≥0.15 mg/mL [range 0.24-54.64 mg/mL]; 69.6 % (80/115) had ≥1.0 mg/mL and 14% (16/115) showed concentrations ≥5.0 mg/mL. The vaccine elicited geometric mean concentrations (GMC) of 4.0, 1.6, 1.4 and 2.4 mg/mL in groups of 7-12, 13-24, 25-48 and 49-93 month-old respectively.Conclusions: PRP-T vaccination in this group of Mexican children has resulted in serum IgG concentrations ≥0.15 mg/mL, suggesting that Hib immunization has conferred protection against invasive disease.

Epidemiology and outcomes of bacterial meningitis in Mexican children: 10-year experience (1993–2003)

“…Recent serological evidence has shown that the pentavalent vaccination in a well defined cohort of children between the ages of 7 and 93 months, demonstrated serum IgG concentrations >0.15 mg/ml. 28 These serological titers have been shown to confer protection against Hib invasive disease. 28 Therefore, the purpose of our study was to define the leading pathogens causing community-acquired meningitis (beyond the neonatal period) in a pediatric population in a major referral pediatric hospital in Mexico City.…”

“…28 These serological titers have been shown to confer protection against Hib invasive disease. 28 Therefore, the purpose of our study was to define the leading pathogens causing community-acquired meningitis (beyond the neonatal period) in a pediatric population in a major referral pediatric hospital in Mexico City. The causative organisms found in a particular region vary with the patient's age and general health, and with the immunization status of the community.…”

Immunoglobulin G Avidities in Infants in Mexico after Primary Immunization with Three Doses of Polyribosylribitol Phosphate-Tetanus ToxoidHaemophilus influenzaeType b Vaccine

“…1). A similar trend was seen for age-stratified sera from Mexico City (13). In contrast, the GMCs of sera from Guadalajara increased in an age-dependent manner ( Table 2).…”

“…PSAB-90 serum was used as a quality control. Data for IgG concentrations from Mexico City sera have been previously described (13).…”

“…Concentrations and avidities of anti-PRP IgG were assessed on serially diluted sera by using ELISA and ELISA-based elution assays with 0.15 M sodium thiocyanate (NaSCN) (2,13,26). PSAB-90 serum was used as a quality control.…”