BCG Vaccination

History

(1) Aim

(2) Vaccine

• BCG is the only widely used live bacterial vaccine.
• Consists of living attenuated bovine strain of tubercle bacilli.
• Derived from the original Calmette strain.
• Many substrains have evolved due to different production methods.
• WHO recommended strain: "Danish 1331" (used at BCG Laboratory, Guindy, Chennai since January 1967).
• Quality control: International Reference Centre at Copenhagen.

(3) Types of Vaccine

1. Liquid (fresh) vaccine
2. Freeze-dried vaccine - more stable, superior keeping quality; present-day vaccines are distributed in this form.

• Stable for several weeks at ambient tropical temperature.
• Up to 1 year if kept away from direct light and refrigerated at below 10°C.
• Must be protected from light during storage (wrapped in double layer of red or black cloth).
• Normal saline is the recommended diluent (distilled water may cause irritation).
• Reconstituted vaccine must be used within 3 hours; leftover vaccine must be discarded.

(4) Dosage

(5) Administration

• Route: Strictly intradermal using a "Tuberculin" syringe (Omega microstat syringe with 1 cm, 26-gauge intradermal needle).
• Syringe-and-needle technique is the most precise method.
• Other methods (bifurcated needle, dermo-jet) are less accurate.
• Subcutaneous injection increases risk of abscess formation.
• Site: Just above the insertion of the left deltoid muscle (left upper arm).
• Skin must not be contaminated with antiseptic/detergent; if alcohol is used, it must evaporate before injection.
• No other injection should be given into the BCG-vaccinated arm for at least 6 months.

(6) Age Policy

• India (high-TB prevalence countries): BCG given very early in infancy:
  • At birth (for institutional deliveries), OR
  • At 6 weeks simultaneously with DPT and polio
• BCG given early in life provides high protection, especially against:
  • Severe forms of childhood tuberculosis
  • Tuberculous meningitis
• Low-prevalence countries: Restriction to high-risk groups (hospital personnel, tuberculin-negative contacts of TB cases especially MDR-TB).

(7) Normal Phenomena After Vaccination

(8) Complications

1. First: Aspiration
2. If unsuccessful: Incision + local applications of PAS or INH powder (daily)
3. No systemic INH needed
4. Patient should be reassured of harmless nature

(9) Protective Value

• Duration of protection: 15 to 20 years.
• Mechanism: Local BCG infection generates immunity associated with tuberculin hypersensitivity.
• First prospective controlled trial: 80% effectiveness over 20 years.
• Range of protection in various trials worldwide: 0 to 80% (highly variable).
• South India trial found poor protection, possibly due to prior exposure to non-tuberculous environmental mycobacteria (e.g., M. vaccae, M. non-chromogenicum) conferring partial immunity and masking BCG benefit. M. kansasii and M. scrofulaceus have an antagonistic action against BCG.
• Infants and young children vaccinated before contact with environmental mycobacteria do derive protection.
• WHO holds it unreasonable to stop current BCG vaccination programmes.

(10) Revaccination

• Duration of protection is still disputed even 90 years after vaccine development.
• BCG revaccination is NOT included in India's official EPI (Expanded Programme on Immunization) schedule.
• Booster doses are not routinely indicated.

(11) Contraindications

• Generalized eczema or infective dermatosis
• Hypogammaglobulinaemia
• Known/suspected congenital immunodeficiency
• Leukaemia, lymphoma, or generalized malignant diseases
• Patients under immunosuppressive treatment (corticosteroids, alkylating agents, antimetabolites, radiation)
• Symptomatic HIV infection
• Pregnancy

(12) Direct BCG Vaccination

• Direct BCG vaccination (without prior tuberculin test) is India's national policy.
• Allows faster, more complete coverage at lower cost.
• No adverse effects reported in tuberculin-positive reactors.
• Best practice: administer BCG during infancy before contact with environmental mycobacteria.

(13) Impact

• BCG is less effective than active case-finding and chemotherapy.
• Offers only partial protection.
• A 1982 WHO Expert Committee concluded BCG can prevent tuberculosis in uninfected individuals but has only relatively small epidemiological effect on overall risk of infection in the community.

(14) BCG Vaccination and HIV Infection

• Previous WHO recommendation: In high TB-burden countries, BCG should be given to all healthy infants at birth unless the child had symptomatic HIV infection.
• Revised recommendation (GACVS): Children known to be HIV-infected, even if asymptomatic, should NOT be immunized with BCG vaccine, because:
  • HIV-infected children vaccinated at birth who later developed AIDS were at increased risk of disseminated BCG disease.
  • Benefits of preventing severe TB are outweighed by risks.
• However: Most infants born to HIV-infected mothers are themselves uninfected (due to PMTCT interventions) and would benefit from BCG.
• Accurate HIV diagnosis in the first year of life is technically challenging and expensive; WHO recommends HIV testing at around 6 weeks of age, but this is often after BCG has already been given.

(15) Combined Vaccination

• BCG may be given simultaneously with:
  • Oral polio vaccine
  • DPT vaccine (in a different arm) - without reducing immune responses or increasing complications
• Mixed vaccines containing BCG have not yet been introduced.

Criteria for Switching from General to Selective BCG Vaccination ("Low Endemicity" Criteria)

• (a) Average annual notification rate of smear-positive pulmonary TB < 5 per 100,000
• (b) Average annual notification rate of tubercular meningitis in children under 5 years < 1 per 10 million population over previous 5 years
• (c) Average annual risk of TB infection < 0.1%

Summary

BCG vaccination is a fundamental component of a national tuberculosis programme. Despite contradictory trial evidence, BCG plays a valuable role in preventing severe forms of childhood tuberculosis - especially meningitis and miliary tuberculosis. BCG is part of WHO's Expanded Programme on Immunization (EPI). The greatest need remains in developing countries where TB is still a major health problem.

• Park's Textbook of Preventive and Social Medicine, pp. 231-232

Recent Clinical Guidelines: BCG Vaccination in HIV-Positive Infants

Overview of the Core Problem

WHO / GACVS Current Recommendations (Updated December 2025)

Rationale Behind These Recommendations

1. Disseminated BCG disease risk approaches 1% in HIV-positive infants - data from Argentina and South Africa. This is enormously higher than the <1 per million risk in immunocompetent infants.
2. HIV severely impairs BCG-specific T-cell responses in the first year of life - meaning BCG may provide little or no protection against TB in these infants, removing the benefit side of the risk-benefit equation.
3. HAART/ART may reduce dBCG disease rate and immune reconstitution inflammatory syndrome (IRIS) risk, supporting the "delay-until-stable-on-ART" strategy.
4. Early virological testing (recommended by WHO at ~6 weeks of age) is often technically demanding and expensive in high-burden settings, and is frequently done after BCG has already been administered.

The Practical Dilemma in Low-Resource Settings

• BCG vaccination should continue at birth for all infants regardless of HIV exposure, given the high TB endemicity in such populations.
• Close follow-up of infants known to be born to HIV-infected mothers is mandatory to detect and treat any BCG-related complications early.
• Where adequate HIV services exist (early virological testing + rapid ART initiation), BCG should be deferred until HIV status is confirmed.

Recent PubMed Evidence

Comparison: Park's Textbook vs. Current Guidelines

Summary

• Known HIV-infected infant = BCG contraindicated, even if asymptomatic
• Unknown status in a high-burden setting = vaccinate at birth, follow up closely
• HIV-exposed but confirmed uninfected = vaccinate normally
• HIV-infected but stable on ART (CD4% >25%) = BCG can be given

Cardinal Symptoms of Tuberculosis

Respiratory (Pulmonary) Symptoms

1. Cough

• The most common and earliest symptom
• Initially dry and non-productive, progressing to productive (purulent or mucoid sputum) as cavitation develops
• Chronic cough lasting >2-3 weeks is the key screening threshold
• Cough may develop late in primary TB, usually only after tubercle cavitation

2. Hemoptysis (Blood in Sputum)

• Ranges from blood-streaked sputum to frank hemoptysis
• Indicates cavitation or erosion of a blood vessel by the TB lesion
• One of the most specific "alarm" symptoms that should trigger immediate TB workup
• Described across all major textbooks as a cardinal feature

3. Chest Pain

• Usually pleuritic in nature - sharp, worsening on breathing/coughing
• Suggests pleural involvement (pleuritis or pleural effusion)
• May also arise from extensive parenchymal disease

4. Dyspnea (Breathlessness)

• Occurs with extensive lung disease, pleural effusion, or miliary TB
• Usually a later feature in the course of disease

Constitutional (Systemic) Symptoms

5. Fever

• Characteristically low-grade with an evening rise in temperature (pyrexia of insidious onset)
• Often described as a "diurnal fever" - temperature peaks in the late afternoon/evening
• The patient may be unaware of fever, only noticing the associated night sweats

6. Night Sweats

• Drenching night sweats - the patient wakes soaked
• Caused by the evening fever and its subsequent defervescence overnight
• Highly characteristic of TB and other chronic granulomatous/infectious diseases

7. Weight Loss and Anorexia

• Progressive, unexplained weight loss
• Anorexia (loss of appetite) typically precedes the weight loss
• In advanced disease, leads to frank cachexia (wasting)
• Caused by cytokine-driven catabolism (TNF-α, IL-1, IL-6) and reduced caloric intake

8. Fatigue and Malaise

• Generalized weakness, lassitude, and easy fatigability
• Often the earliest and most subtle constitutional complaint
• Patients frequently attribute it to overwork or stress, delaying presentation

Summary Table

Primary vs. Reactivation TB - Symptom Differences

• Tintinalli's Emergency Medicine, p. 796

Classic "Alarm" Triad for TB Screening

Hemoptysis + Night sweats + Weight loss

• Tintinalli's Emergency Medicine: "Clues that suggest tuberculosis include hemoptysis, night sweats, and weight loss."
• Textbook of Family Medicine: "Cough, hemoptysis, night sweats, fever, and weight loss suggest the need to investigate for tuberculosis."

Extrapulmonary TB - Additional Cardinal Features by Site

A Note on Atypical Presentations

• Tietz Textbook of Laboratory Medicine: "Typical signs and symptoms of tuberculosis may be absent in individuals with advanced AIDS, resulting in a delay in diagnosis."

• Dose: 0.1 ml standard / 0.05 ml for newborns <4 weeks
• Scar: 4-8 mm, appears by 6-12 weeks
• Mantoux positive: by 8 weeks (max 14 weeks)
• Complications: Lymphadenitis 1-10%, disseminated <1/million
• Duration: 15-20 years protection
• Efficacy: 0-80% (variable) - first trial showed 80%

Resurgence of Diphtheria

What is the "Resurgence"?

Historical Context

Causes of Resurgence - Park's Textbook Framework

"These epidemics are largely due to: (1) decreasing immunization coverage among infants and children, (2) waning immunity to diphtheria in adults, (3) movement of large groups of population, and (4) an irregular supply of vaccine."

• Park's Textbook of Preventive and Social Medicine

1. Declining / Inadequate Vaccination Coverage

• The most fundamental cause
• Low DTP3 coverage leaves large cohorts of unprotected children
• Incomplete primary series (1-2 doses only) gives partial and unreliable protection
• In developing countries: insufficient supply, poor cold chain, low uptake due to poor health literacy, negative sociocultural/religious beliefs

2. Waning Immunity in Adults

• Childhood vaccination confers protection that fades over time
• A landmark 2022 systematic review and meta-analysis (Gao et al., Journal of Infectious Diseases) confirmed evidence of waning post-vaccination immunity for both diphtheria and pertussis, while tetanus and polio vaccines provided sustained protection [PMID: 34543411]
• Adults who received childhood DTP but no boosters become susceptible over decades
• This creates a pool of susceptible adults, explaining the age-shift seen in outbreaks: cases are increasingly in older children, adolescents, and adults rather than infants

3. Population Movement and Displacement

• Mass migration, refugee crises, and conflict-driven displacement break immunization chains
• Overcrowding in camps and urban slums facilitates transmission
• Current example: Southern Algeria - high national DTP coverage (98%) but resurgence in border regions due to mass displacement from neighboring conflict-affected countries

4. Irregular Vaccine Supply

• Fragile supply chains, especially in conflict zones
• Shortage of Diphtheria Antitoxin (DAT) - critical for treatment but manufactured by very few pharmaceutical companies due to low commercial demand globally
• Nigeria's 2022-2023 outbreak review identified DAT unavailability as the primary driver of high mortality [PMID: 38018582]

5. Reduced Natural Boosting

• Park notes: "Changes in lifestyle allow far less opportunity to maintain natural immunity, such as through frequent skin infection with C. diphtheriae"
• In the past, repeated subclinical exposure naturally boosted immunity; modern sanitation reduces this

6. Vaccine Toxoid vs. Carrier State

• Critically: immunization does not prevent the carrier state - it only prevents disease
• This means even in well-vaccinated populations, C. diphtheriae can circulate silently
• Park's: "The vaccine being a toxoid is not directed against organisms. Therefore immunization does not prevent the carrier state; consequently, the non-immune individuals are not protected by a high level of population immunity."
• Implication: immunization rates must remain very high - there is no herd immunity buffer

Current Global Resurgence (2023-2026) - WHO Data

African Region - Major Ongoing Crisis

• Source: WHO AFRO Disease Outbreak News, November 2025

• Over 50% of suspected cases are unvaccinated or of unknown vaccination status
• Most cases in children under 15 years
• Some outbreaks (South Africa, Algeria) showing adult predominance (70% adults in South Africa) - indicating waning immunity as the driver
• Guinea's CFR of 19-25.8% is among the highest ever recorded in modern outbreaks, driven by DAT unavailability and delayed health-seeking

Yemen and Middle East

India

Why Diphtheria is Particularly Prone to Resurgence

Control Measures (Park's Textbook)

Case Management

• Diphtheria Antitoxin (DAT): Given immediately without waiting for lab confirmation
  • Mild/early disease: 20,000-40,000 units
  • Moderate nasopharyngeal: 40,000-60,000 units
  • Severe/late (≥3 days): 80,000-100,000 units
  • Always give 0.2 ml subcutaneous test dose first (horse serum allergy check)
• Antibiotics: Penicillin or erythromycin for 5-6 days (clears throat of organisms, reduces toxin production)
• Isolation: Minimum 14 days OR until 2 consecutive negative throat/nasal swabs 24 hours apart

Contact Management

• Throat swabs + immunity status check
• Booster within 5 years? → No action needed
• Booster >5 years ago? → Give booster only
• Non-immunized? → Prophylactic penicillin/erythromycin + 1,000-2,000 units DAT + active immunization
• Daily surveillance for ≥7 days

Community - Prevention

• Primary immunization of all infants as early as possible (DPT series)
• Booster doses every 10 years throughout life
• Use of Td (tetanus-diphtheria) vaccine rather than monovalent tetanus toxoid to maintain adult diphtheria immunity
• Catch-up vaccination beyond 5 years of age in outbreak settings
• Strengthening cold chain and vaccine supply

Key Exam Points on Diphtheria Resurgence

1. Classic example: FSU epidemic 1990-1997 (157,000 cases) - gold standard for resurgence due to immunization collapse
2. Four causes (Park's): Low coverage + waning adult immunity + population movement + irregular vaccine supply
3. Critical point: Diphtheria toxoid does NOT prevent carriage → no herd immunity → requires near-100% coverage
4. Age shift: Outbreaks now affect adults and adolescents (not just children) due to waning immunity
5. Treatment bottleneck: DAT is scarce globally - manufactured by few companies
6. Waning immunity confirmed: Systematic review (Gao et al. 2022, J Infect Dis) shows diphtheria and pertussis immunity wanes post-vaccination; tetanus and polio do not [PMID: 34543411]
7. Current crisis: African Region 2023-2026 - >57,000 cases, CFR up to 25.8% in Guinea

Occupations at Higher Risk of COVID-19 Exposure and Preventive Measures

Why Occupation Matters

1. Public-facing work (contact with many people)
2. Working indoors (poor ventilation, aerosol accumulation)
3. Working in close physical proximity to others (< 2 metres)

High-Risk Occupations - Classification

Tier 1: Very High Risk (Patient/Confirmed Case Contact)

1. Healthcare Workers (HCWs)

• Doctors, nurses, paramedics in COVID wards, ICUs, emergency departments
• Anaesthesiologists/ICU intensivists performing aerosol-generating procedures (AGPs): intubation, bronchoscopy, suctioning, nebulization, CPR
• Laboratory technicians handling respiratory samples (RT-PCR testing)
• Radiographers / medical imaging operators
• Mortuary and post-mortem staff (body fluids, aerosols)
• Ambulance and pre-hospital emergency workers

2. Social Care Workers

• Nursing home / residential care facility staff (elderly residents = high fatality risk)
• Disability care workers
• Home health aides and personal carers

Tier 2: High Risk (Essential Frontline Workers)

3. Education Workers

• Teachers and school staff (crowded, indoor, close contact with children who may be asymptomatic carriers)
• Childcare workers and early childhood educators
• Consistently cited across studies as having elevated COVID risk - reported in Denmark, UK, and multiple other countries

4. Food Supply Chain Workers

• Meat processing / poultry plant workers - notorious super-spreader environments (cold, humid, crowded, loud = shouting, poor ventilation)
• Food preparation staff (chefs, kitchen workers)
• Food products machine operators
• Grocery store / supermarket staff (customer-facing, high-contact)

5. Transportation Workers

• Public bus and rail drivers (enclosed spaces, multiple passengers)
• Taxi/rideshare drivers
• Airline crew (recirculated air, confined space)
• Truck and delivery drivers (loading docks, shared cabs)
• Study in 6 Asian countries identified drivers and transportation staff among the most-infected non-healthcare groups.

6. Retail and Customer Service Workers

• Supermarket cashiers, sales staff
• Pharmacists and pharmacy technicians
• High public-facing exposure with variable masking compliance by customers

7. Protective Services and Security Personnel

• Police officers, prison officers
• Security guards
• Reported in UK data as having elevated COVID-19 mortality risk

8. Waste Management and Sanitation Workers

• Handle potentially contaminated materials
• Work in proximity with multiple public spaces

Tier 3: Moderate Risk (Non-Essential but High-Exposure Settings)

• Construction workers (shared tools, shared transport, crowded worker accommodation)
• Personal services (barbers, beauticians, spa workers - close face-to-face contact)
• Religious leaders / clergy (congregational settings)
• Journalists and media personnel (field reporting in crowded settings)

OSHA Hierarchy of Controls Framework for COVID Prevention

Elimination → Substitution → Engineering Controls → Administrative Controls → PPE

Prevention Measures by Category

1. Engineering Controls (Physical/Environmental)

2. Administrative Controls (Policy and Workflow)

3. Personal Protective Equipment (PPE)

4. Hand Hygiene and Surface Decontamination

• Alcohol-based hand rub (ABHR) with ≥60% ethanol at all entry/exit points
• Soap and water for visibly soiled hands (≥20 seconds)
• Regular disinfection of high-touch surfaces: door handles, elevator buttons, cash registers, patient trolleys, shared equipment
• Park's: "Clean and disinfect frequently touched surfaces daily with household disinfectant containing diluted bleach"

5. Vaccination - Priority Group Strategy

6. Occupational Health Surveillance

• Regular serological/PCR monitoring of HCW cohorts
• Return-to-work protocols after COVID illness (including Long COVID assessment)
• Mental health support - HCWs and essential workers experienced significant burnout, PTSD, and moral injury during the pandemic
• Recognition of COVID-19 as an occupational disease (Poland formal guidelines, 2023) enables compensation and legal protection [PMID: 38104343]

Summary: Risk Stratification and Matched Prevention