Age-dependent decrease of anti-HBs titers and effect of booster doses using 2 different vaccines in Palestinian children vaccinated in early childhood

Abstract

Immunization against hepatitis B virus (HBV) has proven to be highly effective and led to significant reduction of new infections worldwide. However, protective immunity measured by anti-HBs titers may decrease to critical levels in the years after basal immunization, particularly in case of exposure to HBV variants different from the vaccine strain. We tested 400 Palestinian children between one and 19 years of age for their anti-HBs titer, challenged the immune memory of those with low or absent anti-HBs with 2 types of hepatitis B vaccines and determined thereafter the anti-HBs titer. At the age of one, 92.2% of the children presented with protective anti-HBs titers (≥10 mIU/ml) with the majority having ≥100 mIU/ml. Protective immunity was still high at ages 2 (87.5%) and 4 (95%), declining by age 5 and 6 (from 69.2% to 66.7%) and down to an average of 39.8% between the ages of 7 and 19. 160 children with a nonprotective or low immune response challenged with either the yeast-derived Engerix-B or the mammalian cell-derived preS1-containing Sci-B-Vac vaccine showed an anamnestic immune response. 92.4% and 85.9% of the children challenged with one dose Sci-B-Vac and Engerix-B presented with anti-HBs titers >100 mIU/ml respectively. Our results reveal that vaccine-induced protective anti-HBs titers against HBV decrease rapidly beyond the age of 6 in Palestinian children, but can be strongly enhanced with a single booster vaccine dose, independent of brand and antigen composition. Our data suggest that a booster vaccine dose against HBV during school years may be useful.

Keywords:

• Hepatitis B Anti
• vaccine-HBs
• protective immunity
• Engerix-B
• Sci-B-Vac
• anamnestic immune response

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Acknowledgments

We would like to thank the following people for their help in recruiting children and drawing blood: The team of the Central Laboratory-MICH, the team of Virology Research Laboratory-Al-Quds University and the UNRWA clinic-Bab Ezzawyeh-Jerusalem. Special thanks to Dr. Elias Habash-UNRWA, West Bank, Nayfeh Ayesh, Pathology laboratory, MICH, Dr. Hatem Khamash, Neonatal Department, MICH, Dr. Iyad Habil, St-John Eye Hospital, Jerusalem, Maysoun Zatari, UNRWA, Hebron, and Mohammad Kurdi, Al-Quds University. Above all, we thank all participating families; without their cooperation this project could not have been completed. Finally we would like to thank Dr. Kae Reynolds from the University of Huddersfield in UK for her critical review of the manuscript.

Funding

This research was supported by German Research Foundation (DFG) grant No. GL595/2-1 to DG and MA.