BCG Vaccine (Bacillus Calmatte Guerin vaccine) is the oldest amongst currently used vaccines (earliest vaccine was small pox, used in 1798), named after its developing scientists – Leon Charles Albert Calmette and Camille Guerin (1921).
Contents of BCG Vaccine: It is a live attenuated vaccine containing 0.1- 0.4 million viable bacilli per dose, In India, Danish strain of Myco. bovis is used to prepare BCG.
Supply & storage of BCG Vaccine: BCG is supplied as a freeze-dried power, generally in multidose, dark-colored ampoules (light sensitive) and should be reconstituted by mixing with sterile normnl saline (not with distilled water, which is irritant) just before use.
Unopened ampoules should be stored in top-most compartment of refrigerator at 2-8°C. As it is extremely heat & light sensitive, reconstituted vaccine must be used within 3 hours.
Schedule of BCG Vaccine: BCG is given preferably at birth or the earliest possible opportunity, till 5 years of age. Primary vaccination or boosters in older children are not recommended in India, due to likelihood of natural infection by this age. However, it may be given in older but tuberculin negative children.
Dose & administration of BCG Vaccine: Irrespective of the age, birth weight or nutritional status, 0.1 ml of reconstituted vaccine is given intradermally over deltoid insertion, conventionally on left side.
Considering the small volume, it is given with a tuberculin syringe and 26- gauge needle, after cleaning the site with sterile wet swab. Spirit or alcohol should not be used for local cleaning as it may affect the viability of vaccine bacilli.
The correct administration of vaccine should raise a wheal of >5 mm over injection site. SC or TM injected vaccine is rapidly cleared by lymphatics and may not induce immune response.
Protective efficacy of BCG Vaccine: Unlike other vaccines, BCG protects by inducing cell mediated immunity rather than humoral immunity.
Protective value of BCG is highly debatable, ranging from 0-80%, due to differences in designs of efficacy-studies. However, it definitely protects (70-80%) against the severe forms e.g. military or CNS tuberculosis.
Bcg vaccine side effects
Bcg vaccine side effects are rare and include —
a) Local secondary infection or keloid formation.
b) Regional lymphadenitis* after 4-8 weeks, due to lymphatic spread of viable bacilli.
c) Disseminated disease is extremely rare but may develop in immunocompromized children.
* Rapidly progressive regional lymphadenitis needs antitubercular therapy with minimum two drugs (INH and Rifampicin) for 4-6 months.
No treatment is necessary for Bcg vaccine side effects non-progressive BCG lymphadenopathy. Surgical drainage should he avoided to prevent sinus formation, though very large nodes may be removed after completion of antitubercular therapy.
Contraindications of Bcg vaccine side effects: There are no absolute contraindications, except —
a) Congenital or acquired immunodeficiency e.g. AIDS.
b) Patients on steroids or cytotoxic chemotherapy.
c) Within 3 months of measles vaccination.
In asymptomatic HIV infected children, Bcg vaccine side effects are not there and should be given as a routine, unless they have any laboratory evidence of immunosuppresion.
Other important issues:
• Natural course of Bcg vaccine side effects is the disappearance of wheel after 20-30 minutes > silent phase for next 3-4 weeks > development of progressive induration after 3-4 weeks > ulceration by 6-8 weeks and> scar formation after 10-12 weeks. In some children, the process of ulceration may be repeated 2-3 times, before eventual scarring.
• Accelerated BCG reaction i.e. development of indiration within 48-96 hours, indicates previous exposure to tubercular infection and has been used as BCG test instead of standard Tuberculin or Mantoux test for presumptive diagnosis of infection (Ch. 10.15).
• The success of BCG vaccine may be judged after 8- 12 weeks, by a) local scar formation, b) Tuberculin conversion, or c) specific tests for cell mediated immunity e.g. Phytohemagglutinin test, Lymphocyte migration inhibition test (LMIT) etc.
• Value of scar: Bcg vaccine side effects scar may disappear after 5-10 years of vaccination and absence of scar does not necessarily mean absence of cell mediated immunity. However, if a child fails to develop the scar after 12 weeks of vaccination, BCG may be repeated on the opposite side.