BCG Vaccine:
Singapore's First-Day Protection Against Tuberculosis

Most Singapore parents born after 1970 have a small round scar on their left upper arm. That scar is the BCG vaccine — Bacillus Calmette-Guérin — the world's most widely administered vaccine, and the first your child receives in this country, usually on the day of birth or within the first few days of life.

What Is Tuberculosis?

Tuberculosis (TB) is caused by Mycobacterium tuberculosis, an airborne bacterium spread by respiratory droplets. It primarily affects the lungs (pulmonary TB) but can disseminate to virtually any organ: lymph nodes, spine, kidneys, brain. Globally, TB remains one of the world's leading infectious disease killers — causing approximately 1.3 million deaths in 2022.

Why Is Singapore's TB Rate Still High?

For a highly developed nation, Singapore's TB burden is notable. Contributing factors:

• High population density — TB spreads more readily in close-contact environments
• Singapore's regional connectivity — ongoing exposure via travellers and migrants from higher-prevalence countries (Malaysia, Indonesia, India, Philippines)
• Foreign worker dormitory settings — where close living conditions facilitate transmission
• Reactivation of latent TB in older residents who were infected before vaccination was widespread

Why Is BCG Given at Birth?

BCG is given as early as possible because it provides its most critical benefit against severe childhood forms of TB:

• TB meningitis — tuberculosis of the brain membranes; rapidly fatal if untreated, devastating neurological sequelae if survived
• Miliary TB — disseminated bloodstream infection spreading TB throughout the body; particularly lethal in infants

BCG provides 70–80% protection against these severe forms. It is less effective against adult-type pulmonary TB — which is why vaccinated adults can still contract and transmit TB, and why Singapore maintains active TB screening programmes.

What Happens After the BCG Injection

The BCG is given as a single intradermal injection into the left upper arm. What follows is a predictable and normal sequence:

1. A small red raised papule at the injection site within 1–2 weeks
2. The papule enlarges and may form a blister or ulcer over weeks 2–6
3. The ulcer crusts over and heals, leaving a small permanent scar
4. The entire process takes 2–3 months

Lymph Node Swelling

A pea-sized swollen lymph node in the left armpit is common and expected — it is your baby's immune system responding to the vaccine. This is normal and will resolve on its own. See a doctor if the node becomes larger than 1cm, red, painful, or develops into an abscess — this may require assessment.