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BCG vaccine (TB)

The BCG vaccine is a live version of TB (like the measles, mumps and rubella vaccines) that has been altered or “attenuated” to be made relatively safe. BCG stands for Bacille Calmette Guérin, named after its discoverers. It has been part of the UK immunisation schedule since 1953. For most of this period, the vaccine has been offered to all 10 to 14 year old schoolchildren, who first had to have a tuberculin skin test, to ensure that they were not already immune to TB. In 2005, the UK policy on BCG vaccination changed, so that the vaccine is now offered to:
  • All babies living in areas with a high rate of TB (with 40 or more new cases a year per 100,000 population)
  • Babies whose parents or grandparents were born in a country with a high rate of TB
  • Babies living with a family member who has had TB recently
  • New immigrants to the UK from countries with a high rate of TB


Though the BCG vaccine has been measured in some studies as having no protective effect at all, in the UK it is probably around 78% effective when given to teenage schoolchildren, and around 64% effective in British Asian babies. Though there is uncertainty how effective the vaccine is in UK babies from other ethnic groups, it does appear to be good at preventing the more serious types of TB such as TB meningitis.

Side effects

Because the BCG vaccine is injected just under the skin, side effects at the site of the injection are common. A lump will normally develop at the injection site (usually on the left upper outer arm). This can become ulcerated and may bleed, or ooze pus, requiring a dressing to be applied. A small permanent scar is normal (see below).

Because BCG is a ‘live’ vaccine, it can cause all the same complications as TB, but much less commonly. Up to 1 in 50, though usually around 1 in 300, vaccine recipients get
swollen and painful lymph nodes (glands) in the neck or armpit; if severe they occasionally become infected, leading to an abscess requiring surgical draining.

The most serious side effect of BCG vaccination is to get a
widespread TB-like infection. This very rare, though occasionally fatal, complication occurs in around 1 in 200,000. It is mainly confined to babies with impaired immune systems, but this may be difficult to detect in the newborn. Various hypersensitivity and skin reactions can also occur.

The BCG, as a live vaccine, should not be given to those with an impaired immune system, including those suspected of being HIV positive. No one who has had TB should be vaccinated, nor should babies who live with someone with active TB.

Tuberculin skin testing before BCG immunisation – the Mantoux test

A skin test is necessary before BCG immunisation for:
  • All adults and children over 6 years of age
  • Babies and children under six years of age who have lived or stayed over 3 months in a country with a high incidence of TB
  • Anyone who has had close contact with someone with TB
  • Anyone with TB in the family within the last 5 years

The Mantoux test involves injecting a tiny quantity of extracts of the TB bacterium (bug) into the forearm. The skin is examined 2-3 days later. It is used as a screening test for tuberculosis infection or disease.

Having a BCG vaccination

The BCG vaccine is given in a different way to all the other common childhood immunisations. The vaccine, usually given into the left upper outer arm, must be injected only just beneath the surface of the skin (intradermally) so that a small lump appears on the skin as the injection is being given. The lump will increase in size over the next few weeks, during which it will scale and crust over; a small ulcer sometimes occurs, which may ooze and require a protective dressing. The lesion then slowly heals over several months resulting in a characteristic flat circular scar.

No further immunisation should be given into the same arm for at least three months.

To download a detailed list of all the vaccines we offer including all their ingredients please follow this link