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Cell mediated immunity in children with scar-failure following BCG vaccination
S H Rani1, V Vijayalakshmi, K Sunil
1Immunology Unit, Bhagwan Mahavir Medical Research Center, Hyderabad.
Insights
BCG scar absence in 10% of vaccinated children, particularly those immunized within 48 hours, does not indicate failed immunization. Most children without a BCG scar still show a positive cellular immune response.
Area of Science:
- Immunology
- Pediatrics
- Vaccinology
Background:
- Bacille Calmette-Guérin (BCG) vaccination is crucial for preventing tuberculosis.
- The presence of a BCG scar is often used as an indicator of successful vaccination.
- Variations in scar formation and their implications for immunity require further investigation.
Purpose of the Study:
- To determine the incidence of BCG-scar failure in BCG-vaccinated children.
- To evaluate the in vitro cellular immune response in children with and without BCG scars.
- To assess the correlation between BCG scar formation and cellular immunity.
Main Methods:
- A four-year prospective cohort observational study was conducted.
- 655 BCG-vaccinated children were followed up to 6 months of age.
- In vitro leukocyte migration inhibition (LMI) tests against PHA/PPD were performed on 228 children.
Main Results:
- BCG scar failure was observed in approximately 10% of vaccinated children.
- Scar absence was highest in infants vaccinated within 48 hours of life.
- A majority of children, irrespective of scar presence, demonstrated a positive in vitro cellular response to PPD.
Conclusions:
- Failure to form a BCG scar does not necessarily indicate a lack of immunization.
- Early BCG vaccination (within 48 hours) is associated with a higher incidence of scar failure.
- In vitro cellular immune response remains a more reliable indicator of BCG vaccine efficacy than scar formation.
Objective:
To find out the incidence of BCG-scar failure, in BCG vaccinated children and assess their in vitro cellular response.
Design:
Four year prospective cohort observational study.
Setting:
Immunization centers at: (a) State Tuberculosis Center; (b) Tuberculosis Association of Andhra Pradesh; and (c) Niloufer Hospital for Women and Children in Hyderabad.
Methods:
Healthy children brought to the immunization centers for BCG vaccination and were followed up till 6 months of age for scar failure. These 655 BCG vaccinated children were classified into three groups based on the age at vaccination: (i) 0 day-1 day; (ii) 2 days-30 days; and (iii) 31 days-90 days. Of these children, in vitro leukocyte migration inhibition (LMI) levels against PHA/PPD were investigated in 228 of them.
Results:
Of the 655 children, 591 (90.2%) showed presence of scar. Out of the three groups, number of children belonging to the first group in whom the scar was absent, was highest. Of 591 children with scar, LMI was performed in 34, 110 and 43 of them in the three different age groups, respectively out of whom 88.2%, 87.2% and 86% had positive response (> or = 20%) to PPD. Of 64 children who failed to develop a scar, LMI was performed in 17, 19 and 5 in three different age groups out of whom 88.2%, 94.7% and 80% had positive (> or = 20%) in vitro response to PPD.
Conclusion:
Scar failure may occur in 10% of BCG vaccinated and is more common with immunization within 48 hours of life. Failure of formation of BCG-scar at the site of BCG vaccination may not necessarily imply failure of immunization because majority of them do elicit positive in vitro LMI response.