A cohort study to evaluate persistence of hepatitis B immunogenicity after administration of hexavalent vaccines.
BACKGROUND
In 2001, two hexavalent vaccines were licensed in Italy (Hexavac, Infanrix Hexa), and since 2002 were extensively used for primary immunization in the first year of life (at 3, 5, 11/12 months of age). In 2005, the market authorization of Hexavac was precautionary suspended by EMEA, because of doubts on long-term protection against hepatitis B virus. The objectives of this study were to evaluate the persistence of antibodies to anti-HBs, in children in the third year of life, and to investigate the response to a booster dose of hepatitis B vaccine.


METHODS
Participant children were enrolled concomitantly with the offering of anti-polio booster dose, in the third year of life. Anti-HBs titers were determined on capillary blood samples. A booster dose of hepatitis B vaccine was administered to children with anti-HBs titers < 10 mIU/ml, with the monovalent precursor product of the previously received hexavalent vaccine. HBsAb titers were tested again one month after the booster.


RESULTS
Sera from 113 children previously vaccinated with Hexavac, and from 124 vaccinated with Infanrix Hexa were tested for anti-HBs. Titers were > or = 10 mIU/ml in 69% and 96% (p < 0,0001) respectively. The proportion of children with titers > or = 100 mIU/ml did also significantly differ among groups (27% and 78%; p < 0,0001).Post-booster, 93% of children achieved titers > or = 10 mIU/ml, with no significant difference by vaccine group.


CONCLUSIONS
Fifteen months after third dose administration, a significant difference in anti-HBs titers was noted in the two vaccine groups considered. Monovalent hepatitis B vaccine administration in 3-year old children induced a proper booster response, confirming that immunologic memory persists in children with anti-HBs titers < 10 mIU/ml. However, long-term persistence of HBV protection after hexavalent vaccines administration should be further evaluated over time.
Giambi
Cristina
C
Communicable Disease Epidemiology Unit, National Centre for Epidemiology, Surveillance and Health Promotion, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy. cristina.giambi@iss.it
Bella
Antonino
A
Barale
Antonella
A
Montù
Domenico
D
Marchisio
Maria
M
Oddone
Maurizio
M
Zito
Salvatore
S
Rapicetta
Maria
M
Chionne
Paola
P
Madonna
Elisabetta
E
Ciofi degli Atti
Marta L
ML
D002675:Child, Preschool; D015721:Diphtheria-Tetanus-Pertussis Vaccine; D005260:Female; D006509:Hepatitis B / Q000276:immunology / Q000517:prevention & control*; D006510:Hepatitis B Antibodies / Q000097:blood* / Q000276:immunology; D017325:Hepatitis B Vaccines / Q000008:administration & dosage / Q000276:immunology*; D006515:Hepatitis B virus / Q000276:immunology*; D006801:Humans; D007117:Immunization, Secondary; D007156:Immunologic Memory / Q000276:immunology*; D007558:Italy; D008297:Male; D011054:Poliovirus Vaccine, Inactivated; D011446:Prospective Studies; D017778:Vaccines, Combined / Q000008:administration & dosage / Q000276:immunology*
D015721:Diphtheria-Tetanus-Pertussis Vaccine; D006510:Hepatitis B Antibodies; D017325:Hepatitis B Vaccines; C426944:Hexavac; D011054:Poliovirus Vaccine, Inactivated; D017778:Vaccines, Combined