Safety and immunogenicity of a pediatric formulation of inactivated hepatitis A vaccine in Argentinean children.
BACKGROUND
Children are a reservoir of hepatitis A virus and must be considered as primary targets of any immunization strategy. The safety and immunogenicity were evaluated for a new formulation of an inactivated hepatitis A vaccine, Avaxim 80 units, containing one-half the antigen dose of the adult formulation.


METHODS
The safety of two doses of this vaccine given 6 months apart was evaluated in an open study in 537 Argentinean children 12 months to 15 years old. Immunogenicity was evaluated at Weeks 0, 2, 24 and 27 in a subgroup of 120 subjects.


RESULTS
Two weeks after the first vaccine dose, >99% of initially seronegative children had seroconverted (titers > or =20 mIU/ml), with a geometric mean titer of 98.5 mIU/ml. Before booster at 24 weeks all subjects had seroconverted. A strong anamnestic response was observed after the second dose at which time the geometric mean titer had increased >35-fold, and antibody titers were consistent with long term protection. Immediate adverse reactions were observed in 3 of 537 (0.6%) subjects after the first dose. Local reactions were mild and transient and did not increase with subsequent doses. Among the systemic events reported during the 7-day follow-up period, 37 cases of fever after the first dose and 22 cases after the second dose were reported. Only 3 cases of fever were clearly related to vaccination (< or =38.2 degrees C) after the first injection, all of which subsided in less than 1 day.


CONCLUSIONS
This study demonstrated the safety and immunogenicity of a pediatric formulation of hepatitis A vaccine in children ages 12 months to 15 years in healthy children ages 12 to 47 months.
López
E L
EL
Infectious Diseases Division, Hospital de Niños Dr. Ricardo Gutiérrez, Buenos Aires, Argentina. eduardolopez@sinectis.com.ar
Del Carmen Xifró
M
M
Torrado
L E
LE
De Rosa
M F
MF
Gómez
R
R
Dumas
R
R
Wood
S C
SC
Contrini
M M
MM
D000293:Adolescent; D001118:Argentina; D002648:Child; D002675:Child, Preschool; D005260:Female; D035922:Hepatitis A Antibodies; D022362:Hepatitis A Vaccines / Q000008:administration & dosage / Q000009:adverse effects* / Q000276:immunology*; D006508:Hepatitis Antibodies / Q000097:blood*; D006507:Hepatovirus / Q000276:immunology*; D006801:Humans; D007117:Immunization, Secondary; D007223:Infant; D008297:Male; D012449:Safety; D015164:Vaccines, Inactivated / Q000008:administration & dosage / Q000009:adverse effects / Q000276:immunology
D035922:Hepatitis A Antibodies; D022362:Hepatitis A Vaccines; D006508:Hepatitis Antibodies; D015164:Vaccines, Inactivated