Antibody Level against Hepatitis B Virus in Term and Preterm Infants Following Three Doses of Pentavalent Vaccine as per EPI Schedule.

Childhood acquisition of Hepatitis B infection significantly increases the risk of chronic liver disease. To prevent this, the World Health Organization (WHO) recommends immunizing infants with three doses of the pentavalent vaccine (DPT + Hib + Hepatitis B) at 6, 10 and 14 weeks of age as part of the Expanded Program on Immunization (EPI). Vaccination schedules may vary based on birth weight and maternal Hepatitis B infection status. Preterm infants, due to their potentially weaker immune status, may require revaccination or booster doses in cases of non-response or poor response. This cross-sectional comparative study was conducted in the Department of Pediatrics, Mymensingh Medical College Hospital, Bangladesh, from October 2017 to September 2019. A total of 118 infants (59 terms and 59 preterm) who had completed the three-dose pentavalent vaccine schedule were included, selected from two EPI centers in Mymensingh city. Anti-HBs antibody levels were assessed six weeks after the third vaccine dose using an ELISA immunoassay kit. The mean anti-HBs levels in preterm and term infants were 143.41±37.81 mIU/mL and 140.96±42.81 mIU/mL, respectively, with no statistically significant difference (p>0.05). A good response (anti-HBs >100 mIU/mL) was observed in 89.8% (53/59) of preterm and 86.4% (52/59) of term infants. Poor responses (anti-HBs 10-100 mIU/mL) were seen in 6.8% (4/59) of preterm and 11.9% (7/59) of term infants. Among infants with a birth weight ≥2500 gm, 87.7% (50/57) showed a good response. Infants weighing 1500-2499 g demonstrated a good response in 88.3% (53/60) of cases. Of the 53 preterm good responders, 86.8% (46) had a gestational age of ≥34 weeks at delivery. In conclusion, the current pentavalent vaccine schedule under EPI produces a good immune response in most infants, with no significant difference between term and preterm infants. Among preterm infants, a better immune response was associated with a gestational age of ≥34 weeks.