Typical time courses and appearance of skin reactions at the site of Bacillus Calmette-Guérin vaccination for infants inoculated at 5-8 months of age.

BACKGROUND

Taiwan increased the Bacillus Calmette-Guerin (BCG) vaccination age from 24 h after birth to 5-8 months of age to lower BCG-related osteitis/osteomyelitis in 2016. However, the sequences of skin changes at the injection site and in the corresponding lymph nodes are unknown for infants vaccinated at an older age.

METHODS

We prospectively collected the photographs of skin reactions within 6 months after vaccination. The type, size, onset time, and duration of the skin reactions were recorded and analyzed.

RESULTS

We enrolled 532 infants. The types and median times at onset of skin reactions were as follows: erythema at week 1, induration at week 3, ecchymosis at week 4, and ulceration at week 6. The peak skin responses were at week 6, with average sizes of 8.4 mm, 7.4 mm, and 8.2 mm for erythema, induration, and ecchymosis, respectively. The duration of induration was long, with 57.6 % and 23 % of the infants still having a response at week 12 and 24, respectively. The rate of induration size ≥ 20 mm was 1.7 % (95 % confidence interval: 0.8 %-3.2 %). Overall, 46.4 % of the infants experienced ulcerative change, with most occurring at week 6 (34.1 %), and 9.5 % and 4.1 % of the infants still had ulceration at week 12 and 16, respectively. Twelve infants (2.3 %) had spontaneous resolution of regional lymphadenitis, with the onset time ranging from week 1 to 12. All infants had developed a scar at the end of follow-up.

CONCLUSION

Our study demonstrates the typical appearance and time courses of skin reactions in infants who received the BCG vaccination at older than 5 months of age. Infants vaccinated at this age may have a more potent skin response with longer induration and ulceration than those vaccinated at birth.