Immunogenicity of heptavalent conjugate vaccine against Streptococcus pneumoniae in premature babies with low birth weight.

Background: There are few studies about immunogenicity and safety of heptavalent pneumococcal-CRM197 conjugate vaccine (PCV7) in low birth weight infants.

Objective: Assessment of immunogenicity following administration of PCV7 in low birth weight children.

Methods: The PCV7 vaccine was administered to 60 infants divided into two groups: 23 children with birth weight <1000 g (Group I); and 37 children with birth weight ≥1000 g (Group II). Serum was collected four times.

Results: Birth weight of children included in the study ranged from 480 g to 2450 g. The primary immunization caused an increase in the average concentration of antibodies for all serotypes in most of the participants, with no significant differences between the groups. However, there were some differences between various serotypes. Group serotypes 6B and 23F were the least immunogenic (≥0.35 μg/mL, Group I vs. Group II - 6B: 78.3% vs. 67,6% p = 0.371 and 23F: 87% vs. 83.8% p = 0.738). Prior to the administration of a booster dose, a significant decrease in antibody titer was observed in all children. The last vaccination resulted in an increased concentration of antibodies in all children in both groups, and the results were significantly higher compared to those measured following administration of three doses of the vaccine.

Conclusion: PCV7 is immunogenic in children with low, very low, and extremely low birth weight. Serotypes 6B and 23F were the least immunogenic, and serotype 14 proved to be the most immunogenic.