BCG reaction in twin newborns: effect of zygosity and chorionicity.

Objective: To study local response to BCG vaccination in twin babies and find out the effect of zygosity andchorionicity on BCG uptake.

Design: Analytical observational study.

Setting: Tertiary hospital.

Methods: Twin pairs born in the hospital were evaluated for zygosity and chorionicity. BCG vaccination was given within 48 hours of birth to babies >/=33 weeks of gestation and birth weight >/= 1500 g. Follow-up was done at 6,10 and 14 weeks. Local response to BCG vaccination was recorded in the form of no reaction, abortive reaction, papule, pustule, ulcer, scab or scar.

Results: One hundred thirty three twin pairs were delivered (16 monochorionic, 117 dichorionic); of which zygosity was determined in 110 pairs (81 dizygotic, 29 monozygotic). Two hundred four twin babies qualified for BCG vaccination. After 14 weeks, local reaction was seen in 84.3% babies and scar formed in 41.2% cases. Five abortive reactors and 20 'true non-reactors' were also found. Intra-pair agreement for local BCG reaction was highly significant in both monozygotic/dizygotic, as well as monochorionic/dichorionic twins (P<0.01). However, monozygotic and monochorionic intrapair agreements were not significantly larger than the dizygotic and dichorionic intrapair agreements(P >/= 0.05), respectively.

Conclusion: Local response to BCG vaccination in twin newborn babies follows same pattern as singletons and there is no effect of zygosity or chorionicity on the uptake.