Immune response to hepatitis B vaccine: An evaluation

Hepatitis B virus infection is a major public health problem in India, and all health-care workers (HCWs) need to be immunized to prevent occupational exposure. This study was done to find the hepatitis B vaccination rates, immune response, and predictors of titer <10 mIU/ml among students and HCWs of a tertiary care institution in the state of Kerala.

This was a cross-sectional study conducted in the Department of Microbiology, Government TD Medical College, Alappuzha, Kerala, India, for a period of 1½ years between January 1, 2016, and June 30, 2017. Vaccination rates were collected through a screening proforma. Of the 1321 participants who filled the screening proforma, 5 ml of blood was collected aseptically from 579 participants who were fully vaccinated (all the three doses of vaccine) and stored at -20°C until antibody to hepatitis B surface antigen (anti-HBs) assay was done using Microlisa (Biorad). Data were analyzed using SPSS for Windows, version 16.0. (SPSS Inc., Chicago, IL, USA) (trial version).

Descriptive data were expressed using frequencies and percentages, and Chi-square test was applied to find the association between antibody titer <10 mIU/ml and independent variables.

Of the 1321 participants who filled up the screening proforma, the vaccination rate was 72.6%. Majority of the participants, i.e. 83.5% of doctors, 81.1% of nurses, 69.7% of students, and 21.4% of technicians, had taken all the three doses of hepatitis B vaccine. Of the fully vaccinated (n = 959) participants, 76.9% had the vaccination during adulthood and only 26.1% had it during childhood. The correlate of protection was defined as the presence of anti-HBs ≥10 mIU/ml. The mean antibody titer was 448 ± 284.97 mIU/ml ranging from 9.8 to 2000. Of the 579 participants whose titer was checked, 71 (12.3%) had a nonprotective titer of <10 mIU/ml. We found that age >35 (odds ratio [OR]: 3.85, 95% confidence interval [CI]: 2.12-6.99]), last dose >10 years (OR: 5.01, 95% CI: 2.94-8.55), no boosters or revaccination (OR: 2.94, 95% CI: 1.42-6.07), and body mass index (BMI) >25 (OR: 2.51, 95% CI: 1.44-3.39) were associated with nonprotective titer.

More than a quarter of the study population who were at high risk of exposure were unvaccinated or partially vaccinated. Even after taking the full course of hepatitis B vaccine, 12.3% had titer <10 mIU/ml. Nonprotective titer was found to be associated with age >35 years, last dose taken >10 years ago, no boosters/revaccination, and BMI ≥25.