Oral polio vaccine influences the immune response to BCG vaccination. A natural experiment

Area of Science:

• Immunology
• Vaccinology
• Public Health

Background:

• Oral polio vaccine (OPV) is typically administered at birth alongside the bacille Calmette-Guérin (BCG) vaccine.
• Variations in OPV availability led to a natural experiment where some infants received only BCG at birth.
• This situation provided an opportunity to study the impact of simultaneous OPV and BCG administration on the immune response to BCG.

Purpose of the Study:

• To investigate the effect of giving oral polio vaccine (OPV) simultaneously with bacille Calmette-Guérin (BCG) vaccine at birth on the subsequent immune response to BCG.
• To compare the in vitro and in vivo immune responses to purified protein derivative (PPD) of Mycobacterium tuberculosis in infants who received both vaccines versus those who received BCG alone.

Main Methods:

• A comparative study involving low-birth-weight (LBW) and normal-birth-weight (NBW) infants.
• Measurement of in vitro cytokine responses (IL-13, IFN-gamma, IL-10) to PPD at 6 weeks of age.
• Assessment of in vivo response to PPD and BCG scar formation at 2 months of age.

Main Results:

• Simultaneous OPV and BCG administration at birth was associated with reduced in vitro cytokine responses to PPD in both LBW and NBW infants.
• Infants receiving OPV with BCG showed significantly lower levels of IL-13 and IFN-gamma, and a trend for lower IL-10.
• In vivo, OPV with BCG was linked to a reduced prevalence of PPD reactions and a tendency for smaller BCG scars.

Conclusions:

• This study provides the first evidence that co-administration of OPV with BCG at birth may down-regulate the immune response to BCG.
• The findings raise concerns about the established practice in low-income countries where OPV and BCG are routinely given together.
• Further research is warranted to understand the long-term implications for BCG vaccine efficacy and public health strategies.