Immunogenicity of a 7-valent pneumococcal conjugate vaccine (PCV7) and impact on carriage in Venezuelan children at risk of invasive pneumococcal diseases.
OBJECTIVE
We evaluated the immunogenicity of the 7-valent pneumococcal conjugate vaccine (PCV7), and its impact on pneumococcal carriage in Venezuelan children at high risk for invasive pneumococcal disease (IPD).


METHODS
82 children (age 2-59 months) with sickle cell anemia (n=22), chronic heart disease (n=19), HIV infection (n=12), immune-suppressive therapy (n=11) and other IPD-predisposing conditions (n=18) were vaccinated with PCV7 according to CDC-recommended age-related immunization schedules. Blood samples were taken to determine the concentration of IgG antibody, and nasopharyngeal swabs were obtained to isolate Streptococcus pneumoniae, before the first vaccine dose and 1 month after completion of the vaccination schedule.


RESULTS
Pneumococcal carriage prior to the first immunization was 27% (n=22), with the most frequently carried serotypes being vaccine serotypes 6B (22%) and 14 (13%). One month after completion of the vaccination scheme pneumococcal carriage was 22% (n=17), dominated by non-vaccine serotypes 19A (24%) and 7F (12%). Before immunization, 65% of the subjects had IgG antibody titers >0.35 μg/mL for five serotypes tested. Post-vaccination, 100% of the subjects showed titers >1.0 μg/mL for all PCV7 serotypes with geometric mean concentrations (GMC) ranging from 1.75 μg/mL (serotype 23F) to 17.16 μg/mL (serotype 14). Children previously colonized with serotype 6B had a significantly lower GMC to this serotype following immunization than children not carrying 6B prior to the first PCV dose (p<0.05).


CONCLUSIONS
PCV7 is highly immunogenic in Venezuelan children at high-risk for IPD. Vaccination was associated with an immediate shift in nasopharyngeal carriage toward non-PCV7 serotypes. Finally, we observed serotype-specific hyporesponsiveness to immunization after natural carriage with the same serotype in high-risk children.
Laboratorio de Tuberculosis, Instituto de Biomedicina, Universidad Central de Venezuela, Caracas, Venezuela. Electronic address: ismaralejandra@gmail.com.
Ismar A
IA
Rivera-Olivero
Departamento de Pediatría, Hospital de Niños "J.M. de Los Ríos", Caracas, Venezuela. Electronic address: beredelnogal@gmail.com.
Berenice
B
Del Nogal
Departamento de Pediatría, Hospital de Niños "J.M. de Los Ríos", Caracas, Venezuela. Electronic address: mdfreitas@gmail.com.
Mariana
M
Fuentes
Departamento de Pediatría, Hospital de Niños "J.M. de Los Ríos", Caracas, Venezuela. Electronic address: cortezrosanna@gmail.com.
Rossana
R
Cortez
Pediatric Immunology and Infectious Diseases, University Medical Center Utrecht, WKZ, Utrecht, The Netherlands. Electronic address: d.bogaert@umcutrecht.nl.
Debby
D
Bogaert
Department of Pediatrics, Laboratory of Pediatric Infectious Diseases, Radboud University Medical Centre, Nijmegen, The Netherlands. Electronic address: p.hermans@cukz.umcn.nl.
Peter W M
PW
Hermans
Laboratorio de Tuberculosis, Instituto de Biomedicina, Universidad Central de Venezuela, Caracas, Venezuela. Electronic address: jacobusdeward@gmail.com.
Jacobus H de
JH
Waard
D000907:Antibodies, Bacterial / Q000097:blood; D002353:Carrier State / Q000453:epidemiology*; D002675:Child, Preschool; D005260:Female; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007223:Infant; D008297:Male; D009305:Nasopharynx / Q000382:microbiology; D011008:Pneumococcal Infections / Q000517:prevention & control*; D022242:Pneumococcal Vaccines / Q000627:therapeutic use*; D012307:Risk Factors; D065288:Serogroup; D013296:Streptococcus pneumoniae / Q000145:classification; D018074:Vaccines, Conjugate / Q000627:therapeutic use; D014687:Venezuela
D000907:Antibodies, Bacterial; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D007074:Immunoglobulin G; D022242:Pneumococcal Vaccines; D018074:Vaccines, Conjugate
High risk children; Immunogenicity; PCV7; Pneumococcal carriage; Venezuela