Inoculation Age of Bacillus Calmette-Guérin Tokyo-172 Strain and Vaccine-related Adverse Reactions in Taiwan Birth Cohort of 2012-2017

Background: In 2016 in Taiwan, inoculation with the Bacillus Calmette-Guérin (BCG) Tokyo-172 vaccine was postponed from 24 hours after birth to 5-8 months of age. We reviewed BCG-induced adverse reactions reported to the Vaccine Injury Compensation Program (VICP) to identify differences between early and delayed BCG inoculation.

Methods: Clinical presentations of BCG-related adverse reactions reported to VICP for the 2012-2017 birth cohort were reviewed until the end of 2019. The correlations between inoculation age and complications were evaluated.

Results: We analyzed 233 BCG adverse reactions, including regional lymphadenitis (33.9%), injection site reactions (35.2%), osteitis/osteomyelitis (27.9%), and distant soft tissue infections (3.0%). The incidence of osteitis/osteomyelitis was lower when vaccination was done after 5 months of age (relative risk [RR], 0.32; 95% confidence interval [CI], .16-.64). Injection site reactions (RR, 8.82; 95% CI, 5.04-15.44) and lymphadenitis (RR, 2.24; 95% CI, 1.44-3.45) were significantly more common in vaccinees older than 5 months. Shorter onset durations of mild adverse reactions (lymphadenitis and injection site reactions) were reported in vaccinees older than 5 months, while no statistical significance was found regarding osteitis/osteomyelitis.

Conclusions: Osteomyelitis and distant soft tissue infection may occur less frequently when BCG inoculation occurs after 5 months of age, although mild adverse reactions can be more frequent, symptom onset times can be shortened. As few severe reactions might occur more than 2 years after BCG inoculation and the policy of delayed BCG inoculation was implemented in 2016, a longer observational period is needed to clarify the exact severe complications decrement.