Introduction
BCG vaccine is a live bacterial vaccine given for protection against tuberculosis, mainly severe forms of childhood tuberculosis. It stands for Bacillus Calmette Gurrain, the strain of bovine tuberculosis used in the vaccine & attenuated by French scientists Calmette & Gurren.
BCG is given any time from birth to 15 days of life along with the zero dose of oral polio vaccine. It is to be given to all children as part of the EPI schedule as recommended by Govt. of India.
Storage And Preparation
BCG vaccine is available as a lyophilized powder in an ampoule. The diluent used is buffered saline that is available separately. It is available in a multidose ampoule containing 20 doses. BCG vaccine stocks can be stored frozen in the freezer compartment. Working stock can be stored in the chiller compartment. Even diluents should be stored in the refrigerator's lower racks at 2-80C.
BCG vaccine ampoules should be cut with a file very slowly & not snapped open because it has a vacuum inside or else the glass will splinter and fly if cut very suddenly. It may be safer to hold the ampoule in a cloth to avoid injury should the glass splinter. Once prepared, the BCG vaccine should be used within 2-3 hours & discarded thereafter.
BCG Vaccine Dosing
BCG vaccine is given intradermally i.e. in the layers of skin using 26 no. needle. It is given conventionally over the left deltoid area (to differentiate it from a smallpox vaccine scar, which was conventionally given over the right deltoid area). 0.1 ml of vaccine is given using a BCG syringe which is 1 ml. glass syringe with steel plunger to identify it so that it is not used for any other purpose. A wheal or swelling of 6 mm is raised above the surface. No spirit or antiseptic should be applied over the site before injection. A good bath with soap and water is enough to clean the local injection site. At the most one can use normal saline to clean the area.
Neither Govt. of India nor the Indian Academy of Pediatrics recommends a booster dose of BCG in India. Some countries like in Gulf recommend one or more booster doses.
BCG Vaccine Efficacy
In a country like ours where tuberculosis is endemic, children catch the germs early in life & develop a primary complex. In children younger than 3-5 years of age, this can spread & lead to severe & serious forms of childhood tuberculosis like tuberculous meningitis, disseminated tuberculosis, miliary tuberculosis, tuberculosis of organs like bones, urinary tract, etc. BCG being a live vaccine itself induces a benign primary complex, which leads to some immunity. Such a child when comes in contact with a patient with tuberculosis can still catch the wild germ and develop primary complex, but the spread will be mostly prevented by previous BCG immunity. Hence such children will not develop serious forms of childhood tuberculosis. Such children when they grow as adults can catch tuberculosis again & develop an adult form of tuberculosis which is a different type of tuberculosis altogether. This adult type of tuberculosis is not prevented by BCG. Hence BCG does not prevent primary complex but prevents the spread of the primary complex & hence the severe forms of childhood tuberculosis. This explains the outcome of the famous Chingleput trial on BCG vaccine efficacy, which failed to show the protective efficacy of BCG against the adult type of tuberculosis.
Incidentally, BCG also cross protects against leprosy & the efficacy is 20%.
Reaction To BCG
Immediately after the BCG vaccine, there is a small swelling at the injection site which persists for 6-8 hours. After that, the swelling disappears & the injection site looks normal. After 6-8 weeks a swelling reappears which looks like a mosquito bite. It grows in size & forms a nodule which breaks open & discharges some fluid & forms an ulcer. The ulcer heals by forming a scar. The whole process takes 2-5 weeks. Some times this process of ulceration & healing recurs 2-3 times. Ultimately the typical puckered scar is formed which remains for a lifetime.
The injection site should not be pressed or rubbed. It should not be fomented. Nothing needs to be applied locally. In fact, a bath with soap and water should suffice even when it has ulcerated.
If ulceration occurs within 7 days of injection, one must report to the doctor, as it may be a sign of tuberculosis in the child.
Site of BCG Vaccine
As we saw before, 1-2% of children develop local BCG lymphadenitis. If that happens following injection over the thigh, it will involve superficial & deep inguinal lymph nodes, which can prove dangerous. Also, by convention BCG scars are looked for over the left arm & hence it is easier to recognize for the doctor when parents do not remember whether BCG was given in the past or not. Hence BCG should only be given over the left arm & nowhere else.
BCG Adenitis
local lymphadenitis can occur due to superadded infection over BCG ulcers. One should try oral antibiotics & anti-inflammatory with good local hygiene (soap & water). If the lymph node does not shrink or disappear, it is true BCG lymphadenitis. In these cases, if the size of the node is less than 10-15 mm, if it is firm, non-painful & not matted; no treatment is required & only observation is required. It will usually disappear on its own in the next few month's time. If the glands are bigger than 15 mm, soft, fluctuating with signs of inflammation or softening, painful and matted, or if already an abscess has formed with or without discharge, treatment is definitely required. One can either remove the entire gland surgically or try a course of anti-tuberculous drugs in form of Isoniazid 5 mg/kg/day & Rifampicin 10 mg/kg/day on empty stomach for a period of 3-6 months.
BCG Not Given at Birth
BCG should be given as early as possible in life before the child comes in contact with tuberculosis. It can be given up to 5 years of age. If it is given beyond 6 months it is preferable to do a prior Mantoux test to see if the patient is already sensitized to tuberculosis. If the patient is already sensitized as shown by positive MT, BCG is not necessary. If prior MT is not done, at least check for an accelerated reaction to BCG in the first week after vaccination which may suggest the presence of tuberculosis in the child.
BCG and Developed Countries
In developed countries like the USA, very few cases of tuberculosis occur. As BCG does not prevent primary complex or the adult type of tuberculosis no benefit will be derived by routine BCG vaccination in such countries. In fact, BCG can interfere with the interpretation of the Mantoux test done subsequently. Hence BCG is not recommended in the USA routinely. With the spread of HIV, the incidence of tuberculosis is rising in the USA. Under such circumstances, they may have to reconsider routine BCG vaccination.
No BCG Scar Post Vaccination
The formation of a scar is neither necessary nor is the only indication of the success of the BCG vaccine. However, it is the only simple & convenient way of determining the success of the BCG vaccine. It may take 3-6 months for the scar to form. If no scar is visible at all after 6 months one needs to do the Mantoux test. If negative, one should give repeat BCG.
Can BCG Be Given With Other Vaccines?
BCG can be given with other vaccines. In fact, BCG is given along with zero doses of OPV & 1st Dose of Hepatitis B vaccine at birth. As measles can depress cell-mediated immunity & as BCG induces cell-mediated immunity BCG should not be given along with measles or MMR
BCG Vaccine - Complications
BCG does not lead to fever. Hence search for another cause & treat accordingly. In 1-2% of vaccinees, local lymphadenitis can occur involving axillary lymph nodes or rarely supraclavicular glands, especially if the injection is given very high overarm. In children with the immune-compromised state like AIDS, BCG can lead to progressive systemic disease.