Abstract:
Background: Infants and young children under the age of 2 years are vulnerable to
Streptococcus pneumoniae infections, especially those who are born in developing countries.
Antibiotic therapy was an effective treatment until resistance to antibiotics emerged, and then
vaccines were developed to assistant with the treatment. The first successful conjugate
vaccine was the 7-valent pneumococcal conjugate which resulted in a decrease in vaccine
serotype IPD in infants and children below the age of two years.
Objectives: The main aim of this study was to assess the saliva and serum antibody
concentration response to pneumococcal capsular polysaccharides in children vaccinated and
unvaccinated.
Design: This is a sub-study within a retrospective analysis of a prospective cohort study on
the safety and immunogenicity of 7-valent pneumococcal polysaccharide-protein conjugate
vaccine (PncCV) and the immunogenicity of a H. influenzae type b conjugate vaccine
(HibCV).
Setting and participation: Infants aged between ≥ 4 and ≤ 10 weeks were enrolled, who only
received BCG and Polio vaccine following birth. Infants were enrolled according to HIV
status during routine antenatal screening in the obstetrics wards of the two hospitals, in
Johannesburg and Cape Town.
Measurements: Saliva IgG and IgA concentrations against pneumococcal capsular
polysaccharides serotype 4, 6B, 7F, 9V, 14, 18C, 19F and 23F were quantified a by multiplex
bead-based assay using the Luminex technology. Serum IgG against polysaccharides
serotype 4, 6B, 7F, 9V, 14, 18C, 19F and 23F were measured by a competitive Enzyme
Linked Immuno-Sorbent Assay (ELISA).
Results: Post three primary vaccine doses, both serum IgG and saliva IgG and IgA antibody
concentrations to vaccine serotypes were protective in children who received the vaccine.
The antibody concentration in children whom did not receive the vaccine was much lower in
comparison to the vaccine group in both serum and saliva to vaccine serotypes (P = 0.0001).
And also high positive correlation (>0.6) was observed of IgG in serum and in saliva
following vaccination.
Conclusion: Pneumococcal conjugate vaccines induce pneumococcal capsular polysaccharide
specific antibodies in both serum and saliva. However, there are differences between the
vaccines’ ability to induce mucosal immune response and there are also serotype specific
differences in the antibody concentrations and in the proportion of positive samples after a
series of vaccinations. The pneumococcal conjugate vaccine in this study was able to induce
mucosal immune memory: the anti-pneumococcal IgA concentrations also increased with age
in the saliva of unvaccinated children.
