BCG vaccination

 

No matter which country you are from if you have a scar on your upper arm, then congrats, you are one of those lucky people to get BCG vaccine. Read on to know more about this important tuberculosis vaccine.

INTRODUCTION

BCG vaccine is a fairly safe vaccine and it can protect you from most infectious disease named tuberculosis (TB) which is caused by bacterium Mycobacterium tuberculosis.

It is a live attenuated vaccine, in this type of vaccine, the microbe remains alive, but is attenuated or weakened, treating with some chemical agents as a result it is no longer pathogenic, but it is still enough to elicit an immune response.

By fighting off this weakened version of the bacteria, your body learns how to identify and defeat it ever comes across it again.

BCG: HISTORY OF WORLD’S FIRST TB VACCINE

BCG literally Means “Bacilli Calmette and Guerin” developed by scientists Albert Calmette and Guerin between 1905 and 1918. It is a attenuated strain of Mycobacterium bovis, which is a etiological agent of cattle TB.

It was first time used in 1921 to vaccinate a boy in Paris, who was protected against TB and grew up perfectly healthy, then further 317 infants were vaccinated with BCG in the following 3 years (1921-1924) ,In 1928 at the conference of the league of Nations in Paris the vaccine was declared to be safe.

In India, WHO recommended Danish 1331 strain of BCG is used. It is prepared in central BCG laboratory Guindy, Chennai.

TYPES OF VACCINE

Liquid form (fresh) - less stable.

Lyophilized form (freeze- dried)- More stable and is recommended for use. Before use, reconstitution of lyophilized form is done by using normal saline, after liquefying it should be administered within 1 hour.   

 

IMMUNIZATION SCHEDULE

BCG FOR BABIES-  It is recommended for babies till birth up to 1 year old.   

BCG FOR ADULTS – It is given to adults 1 ml aged 16 to 35 who are at risk of TB, such as some health care workers, veterinary staff and abattoir workers.

ROUTE OF VACCINATION 

On left upper arm (deltoid region) injected intradermally.

 

EXPOSURE OF VACCINATION

After 2-3 weeks: Papule develops

5-6 weeks: Shallow ulcer develops, crust formation 

6-12 weeks: Permanent tiny round scar of 4-8 mm is formed.

8- 14 weeks: Mantoux test become positive.

Overdose: lesion or scar become larger and irregular in size.

HOW IT PROTECT US ?

The BCG is 80% effective in preventing TB for 15 years.

It is also able to prevent serious forms of tuberculosis such as meningeal, skeletal and miliary form of the disease.

Vaccine stimulates T lymphocytes, and provokes the immunity against the disease.

 

 COMPLICATIONS

-Local abscess, keloid, indolent ulcer formation,.

-Regional lymphadenitis

-Systemic fever and erythema around the site of vaccination.

 

BCG IS NOT RECOMMENDED FOR-

Already vaccinated people

People with positive tuberculin skin test (Mantoux)

Past history of TB

Immunocompromised persons with HIV, on chemotherapy treatment ,steroid taking and who have leukemia or lymphoma.

Pregnant women.

 

ONGOING WORK ON BCG

Government of India  studying BCG vaccine use as Covid booster shot after Covaxin, there have been two trials in India with BCG -1 and BCG -2 by the Indian Council of Medical Research ( ICMR).

BCG- 1)  To evaluate efficacy of BCG in reducing the incidence and severity of Covid in the high risk population .

BCG -2)  To evaluate the effectiveness of BCG vaccine in reducing morbidity and mortality in the elderly individuals Covid hotspots.

WHY DO WE NEED NEW TB VACCINE ?

A clear and urgent need exist for vaccines to reduce the burden of disease in adults, unfortunately, pediatric BCG vaccination does not provide adequate protection against adult pulmonary TB.