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Meningococcal group C and w135 immunological hyporesponsiveness in african toddlers

Helen Findlow1, Samba Sow, Ray Borrow

  • 1Vaccine Evaluation Unit, Health Protection Agency North West, P.O. Box 209, Clinical Sciences Building, Manchester Royal Infirmary, Manchester M13 9WZ, United Kingdom. helen.findlow@hpa.org.uk

Clinical and Vaccine Immunology : CVI
|July 15, 2011
PubMed

Insights

Previous meningococcal ACWY polysaccharide (PsACWY) vaccination in toddlers led to hyporesponsiveness to a subsequent fractional booster dose. This suggests careful vaccine scheduling is crucial for effective meningococcal C and W135 immunization.

Area of Science:

  • Immunology
  • Vaccinology
  • Pediatric Infectious Diseases

Background:

  • Meningococcal vaccines are critical for preventing bacterial meningitis.
  • Understanding immune responses to multi-dose vaccination schedules in toddlers is essential for public health.

Purpose of the Study:

  • To assess the immunogenicity of a fractional booster dose of meningococcal ACWY polysaccharide (PsACWY) vaccine in African toddlers.
  • To investigate potential immunologic hyporesponsiveness following primary and booster vaccination with PsACWY in this age group.

Main Methods:

  • A Phase II clinical study involving African toddlers aged 12-23 months.
  • Participants received primary vaccination with PsA-TT, PsACWY, or Hib-TT, followed by a booster dose 10 months later.
  • Serum bactericidal antibody (SBA) assays were used to measure immune responses to serogroups W135 and C.

Main Results:

  • Toddlers previously vaccinated with a full dose of PsACWY showed significantly lower W135 and C SBA geometric mean titers (GMTs) after a fractional booster dose compared to PsACWY-naïve subjects.
  • W135 SBA GMTs at 7 and 28 days post-booster were 26.1/4.4 for previously vaccinated vs. 861.1/14.6 for naïve subjects.
  • C SBA GMTs at 7 and 28 days post-booster were 4.1/3.2 for previously vaccinated vs. 99/5.9 for naïve subjects.

Conclusions:

  • Primary vaccination with a full dose of PsACWY vaccine in toddlers aged 12-23 months induces immunologic hyporesponsiveness to a subsequent fractional booster dose.
  • This finding highlights the importance of considering prior vaccination history when implementing booster strategies for meningococcal vaccines in young children.

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