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Evaluation of anti diphtheria immunity among Nigerian children aged 6-59 months
A E Sadoh1, E Ayinbuomwan2, I I Osaigbovo3
1Institute of Child Health, University of Benin, Benin City, Nigeria.
Introduction:
The recent outbreak of diphtheria in Nigeria affected mostly unvaccinated children; but a significant proportion of fully vaccinated children were affected prompting questions on level of immunity post vaccination.
Aim:
To determine the seroprevalence of anti-diphtheria antibodies in children aged 6 months to 59 months.
Methods:
In this cross-sectional analytic study conducted in Edo state, Nigeria, 257 apparently healthy children were studied. Following written informed consent, 3mls of blood was drawn. The blood was spun, separated and serum stored at -20 °C until analysis for anti-diphtheria antibodies by ELISA method. Anti-diphtheria IgG antibody levels were log-transformed and categorised as <0.01 IU/mL no protection, 0.01-0.09 IU/mL minimal protection, 0.1-0.9 IU/mL full protection and >1 IU/mL long term protection. Data analysis was done using SPSS with Statistical significance set at p < 0.05. Geometric mean titres (GMT) were calculated. Difference in mean titres was tested using student t test and ANOVA as appropriate.
Results:
There were 158(61.5%) males and 99(38.5%) females. Overall GMT was 0.08 IU/mL. GMT of children younger than 12 months was 0.25 IU/mL and was higher than those of all other age groups p < 0.001. There were 54(21.0%) children with no immunity while only 10(3.89%) children had long term immunity. The age group 36-47 months had the highest proportion 14(51.4%) with inadequate immunity followed by the age group 48-59 months with 14(50%).
Conclusion:
Significant proportions of Nigerian children have inadequate immunity despite having received 3 primary doses of diphtheria containing vaccine. We recommend booster doses in the second year of life.
