Immunogenicity and safety of early vs delayed BCG vaccination in moderately preterm (31-33 weeks) infants

Minimum gestation at which infant can be given BCG (Bacillus Calmette-Guerin) vaccine safely at birth is not clearly defined. Our objectives were the following: to compare Mantoux test after 6 months of BCG immunization in moderately preterm babies (31-33 weeks) vaccinated at birth and 34 weeks post conception age and to compare in above groups:(a) Interferon - gamma (IFN-γ) levels in BCG vaccinated infants who did not react to Mantoux test (b) Local BCG reaction at 6, 10, 14 weeks and 6 months (c) Complications of BCG vaccination. Interventional, randomized comparative trial. Moderately preterm infants (31-33 weeks), 90 in each group. At birth, 180 moderately preterm infants were recruited and randomly allocated into 2 groups. Two ml venous blood was drawn for estimation of IFN-γ levels. Infants were given BCG vaccine within 72 hours of birth and followed up after 2, 4, 6, 10, 14 weeks and 6 months (group 1). Infants were recruited at birth and held up till 34 weeks post conception age (group 2) and then given BCG vaccine and followed up similarly as group 1. At each visit, local BCG reaction, any local or unusual complication and anthropometric measurements were noted. At six months, Mantoux test was done and 2 ml venous blood sample was collected for IFN-γ levels post vaccination. Presence or absence of BCG local reaction, PPD conversion rates and complications were analyzed using Chi square or Fisher's exact test. IFN-γ levels were analyzed by ANOVA. In all 117 infants could be followed till 6 months after BCG immunization in 2 groups, and Mantoux test was positive in 38.4% of them. The rate of Mantoux test positivity was similar irrespective of the age of giving BCG immunization (group 1- 39.1% vs group 2- 37.5%; p > 0.05). IFN-γ levels were significantly raised at 6 months in 60% (n = 21/41) and 65% (n = 15/27) Mantoux negative infants in group 1 and group 2 respectively. The sequence and order of local BCG reaction at 2, 4, 6, 10, 14 weeks and 6 months was in the form of papule, pustule, ulcer, scab and scar. Scar was formed in 94.2% and 89.5% infants in group 1 and group 2 respectively. One infant in group 1 showed abortive reaction (0.85%). Only 3.4% of infants developed lymphadenopathy and was similar in both the groups. Moderately preterm infants (31-33 weeks) exhibited 98.3% immunogenicity after BCG immunization at birth and can be safely vaccinated without any risk of severe complications.