Hepatitis B virus infection is a vaccine preventable infection of liver which remains a key public health
burden globally. The development of Anti-HBs titre greater than or equal to 10 IU/L is considered as
protective immunity and any titre less than 10 IU/L as non-protective following HBV vaccination. There is
no comprehensive and authentic data regarding the immune response even 10 years after the integration of
the HBV vaccine in to the EPI programme in Bangladesh and specifically, in Brahmonbaria district. The
study was also aimed to assess the long term immune response among HBV vaccinated children. Blood
sample from 500 vaccinated children were tested for Anti-HBs, and anti-HBc. Sero negative children were
given 1 dose of HBV vaccine as a booster. Samples from booster vaccine were taken one month later and
tested for anti Hbs titre. Anti HBs titre was found below protective level in about 46.0% (230/500)
participants. Sero-protection rate decreased to 72.2% in 5 to 6 years age group which further decreased to
58.3% in 7 to 9 years age group and increased again to 69.5% in 10 to 12 years age group children. On the
other hand, the mean anti Hbs titre was 97.72 IU/L initially and then increased with the increasing of age
from 165.40 IU/L to 196.67 IU/L. Breakthrough infection of HBV was seen in 1.2% (6/500) participants
measuring by anti HBc which indicated protective efficacy of HBV vaccine was about 98.8% (494/500).
Sero negative participants were given a booster dose; 93.6% (131/140) participants showed boosting of
mean anti HBs titre upto 804.92 IU/L which was below protective level (<10 IU/L) before booster dose.
Anti-HBs titre goes below with the increase of age after vaccination.