Decreased immune response to hepatitis B eight years after routine vaccination in Israel

Although immunization of infants against hepatitis B virus (HBV) is the most effective way to prevent infection, duration of the afforded protection is unknown. Titers of anti-HBV antibodies decline with time, especially during the first few years after vaccination. Anti-HBV antibody levels were measured in the serum of vaccinated children in order to determine the duration of the response afforded by the primary course of HBV vaccine.

The immunity derived from the HBV vaccine was assessed by measuring antibody levels in 122 healthy children who were vaccinated in a routine vaccination program in Israel.

Ninety-four children (77.1%) had detectable antibodies levels (HBsAb titer > or = 10 mIU/ml): 59 (48.4%) of the children had high antibodies levels (HBsAb titer > 100 mIU/ml). Twenty-eight children (22.9%) had undetectable antibodies levels (HBsAb titer < 10 mIU/ml). When the children were divided into three groups according to the time elapsed since vaccination, it was found that the antibody levels declined with time (p < 0.009). Most of the children with undetectable antibody levels belonged to the 5 to 8-y post-vaccination group (36.1% vs 20% and 14.6% for the 2.5 to 5-y and 1 to 2.5-y groups, respectively, p < 0.01). The mean HBsAb declined in relation to the length of time post-vaccination (226.9 +/- 248.2 mIU/ml for 1-2.5 y post-vaccination, 199.0 +/- 235.7 mIU/ml for 2.5-5 y and 90.4 +/- 138.5 for 5-8 y, p < 0.05). No correlation was found between HBsAb titers and gestational age, birthweight and parental origin, although females generated higher mean antibody levels than males (207.3 +/- 217 mIU/ml vs 141.9 +/- 218.9 mIU/ml, p < 0.05).

Our data demonstrate a steady decline in anti-HBV titers over time after routine vaccination against HBV in Israel. The most significant decline occurred 5-8 y post-vaccination.