Immunogenicity and reactogenicity of Avaxim (160 AU) as compared with Havrix (1440 EL.U) as a booster following primary immunization with Havrix (1440 EL.U) against hepatitis A.
BACKGROUND
Hepatitis A vaccination is recommended for travelers from the UK to areas of moderate or high endemicity. Two licensed hepatitis A vaccines are now available in the UK, and this trial was undertaken to determine whether Avaxim can be used as a booster following a primary course of Havrix.


METHODS
One hundred and eighty-five subjects were randomized to receive a booster dose of either Avaxim (n=92) or Havrix (n=93), 6 to 7 months after a primary dose of Havrix. Subjects were observed for 30 minutes for immediate reactions and subsequently completed a diary card for a further 2 weeks. Serology samples for HAV antibody titers were taken at 28 6 7 days later.


RESULTS
One month following the booster dose, all subjects in both treatment groups achieved HAV antibody titers >= 20 mIU/mL. In the Avaxim group, geometric mean titer (GMT) values increased from 642 mIU/mL (97.5% CI 330-1250 mIU/mL) to 6669 mIU/mL (4566-9740 miu/mL), compared with 739 mIU/mL (379-1443 mIU/mL) at baseline to 4460 mIU/mL (2880-6908 mIU/mL) following the administration of Havrix. The increase in GMT following the administration of Avaxim was significantly greater than that following Havrix (p=.02). Eight percent of subjects reported pain at the injection site following a booster dose of Havrix, compared with none following Avaxim. This difference in reactogenicity was statistically significant (p=.01). In all other respects, both preparations were safe and equally well tolerated.


CONCLUSIONS
Either Avaxim or Havrix may be given as a booster dose of hepatitis A vaccine when Havrix has been administered as the primary dose.
Academic Unit of Travel Medicine and Vaccines, The Royal Free Hospital School of Medicine, London, United Kingdom.
J N
JN
Zuckerman
C T
CT
Kirkpatrick
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M
Huang
D000293:Adolescent; D000328:Adult; D016009:Chi-Square Distribution; D005260:Female; D006506:Hepatitis A / Q000276:immunology / Q000517:prevention & control*; D022362:Hepatitis A Vaccines; D017957:Hepatitis A Virus, Human / Q000276:immunology*; D006508:Hepatitis Antibodies / Q000276:immunology; D006801:Humans; D007115:Immunization Schedule; D007117:Immunization, Secondary; D008297:Male; D008875:Middle Aged; D011863:Radioimmunoassay; D016037:Single-Blind Method; D018709:Statistics, Nonparametric; D014195:Travel; D015164:Vaccines, Inactivated / Q000008:administration & dosage*; D014761:Viral Hepatitis Vaccines / Q000008:administration & dosage*
D022362:Hepatitis A Vaccines; D006508:Hepatitis Antibodies; D015164:Vaccines, Inactivated; D014761:Viral Hepatitis Vaccines