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Low seroconversion rates to measles vaccine among children in Nigeria
F D Adu1, O A Akinwolere, O Tomori
1College of Medicine, University of Ibadan, Nigeria.
Insights
Nigerian measles immunization vaccine effectiveness varied significantly by vaccine titre. Higher titres correlated with better immune response, but most vaccines did not meet World Health Organization standards.
Area of Science:
- Immunology
- Public Health
- Vaccinology
Background:
- The Nigerian Expanded Programme on Immunization (EPI) aims to provide essential vaccines.
- Measles immunization is a critical component of child health initiatives.
- Assessing vaccine efficacy is crucial for public health program success.
Purpose of the Study:
- To evaluate the effectiveness of measles immunization within Nigeria's EPI.
- To determine the relationship between measles vaccine titre and seroconversion rates.
- To assess compliance with World Health Organization (WHO) vaccine standards.
Main Methods:
- A cohort of 150 children receiving measles vaccine at the Institute of Child Health, University of Ibadan, was studied.
- Seroconversion rates were measured post-vaccination.
- Vaccine titres were analyzed and compared to WHO standards (log 10(-3) TCID50).
Main Results:
- Overall, 54.7% (82 out of 150) of children seroconverted.
- A direct correlation was observed between vaccine titre and immune response.
- Vaccines with lower titres (10(-1) to 10(-2.5)) showed significantly lower seroconversion rates (0-47.6%).
- Vaccines with higher titres (10(-2.7) to 10(-3.4)) demonstrated higher seroconversion rates (87.5-100%).
- Only one vaccine met the WHO minimum titre standard.
Conclusions:
- Measles vaccine titre is a critical determinant of immunogenicity in the Nigerian context.
- The majority of measles vaccines used in this study did not meet WHO standards, potentially impacting program effectiveness.
- Ensuring vaccines meet required titres is essential for successful immunization programs.
Abstract:
The Nigerian Expanded Programme on Immunization (EPI) was assessed with particular reference to measles immunization. Of 150 children who received measles vaccine at the Institute of Child Health, University of Ibadan, Nigeria, 82 (54.7%) seroconverted. The immune response was directly related to the titre of the vaccines used. Vaccines whose titres were 10(-1) to 10(1.7) stimulated immune responses in 0-25% of vaccinees, those with titres in the range 10(-2.1) to 10(-2.5) stimulated responses in 12-47.6%, while those with titres of 10(-2.7) to 10(-3.4) stimulated responses in 87.5-100% of vaccinees. Only one of the vaccines used had a titre that met the minimum WHO required standard of log 10(-3) TCID50 at the point of vaccination.