Immune responses to vaccine-preventable diseases among toddlers and preschool children after primary immunization and first booster in Northwestern Algiers, Algeria

Abstract

ObjectivesTo determine immune responses to selected vaccine-preventable communicable diseases: pertussis, diphtheria and Haemophilus influenzae type b (Hib1) in Algerian toddlers and preschool children after primary vaccination and first booster, recruited from three local healthcare facilities in Northwestern Algiers.MethodsThe information of demographic characteristics and vaccination status were collected for each subject by questionnaire. Specific antibody levels and Hib antibody avidity were determined using commercial ELISA kits.ResultsA total of eighty-one subjects aged between 19 and 55 months were studied. Almost all subjects were fully protected against diphtheria (76/81; 93.83%; 95% CI2: 86.35–97.33) and invasive Hib disease (29/30; 96.67%; 95% CI: 83.33–99.41), while only 20/78 (25.64%; 95% CI: 17.26–36.31) had anti-PT3 (pertussis toxin) antibody levels above 25 IU/ml. A significant decrease of anti-PT antibody levels was observed until the age of 36 months (p = 0.02). GMTs4 (geometric mean titers) of anti-PT antibodies were low, but remain significantly higher in children ≤36 months of age (p = 0.02). Both GMT and rates of ≥0.15 μg/ml, ≥1 μg/ml, and ≥5 μg/ml titers were significantly higher in Hib-vaccinated subjects (p < 0.01). Relative Hib-avidity index (≥50%) and GMAI5 (geometric mean avidity index) were high in both Hib-vaccinated and -unvaccinated groups.ConclusionsAs shown in the present study, young children were fully protected against diphtheria and Hib, but showed low immunity to pertussis. Further sero-epidemiological studies including a large number of subjects with a wider range of age are needed to explore the immunity level in older children, adolescents and adults.

Evaluation of the Potency of the Pertussis Vaccine in Experimental Infection Model with Bordetella pertussis: Study of the Case of the Pertussis Vaccine Used in the Expanded Vaccination Program in Algeria

“…The introduction of pertussis vaccines has strongly reduced the incidence of morbidity and mortality of the disease, particularly in infants and young children [7][8][9]. Currently, two types of vaccines are available, whole-cell vaccines and acellular vaccines (DTaP) are obtained from purified bacterial components.…”