Kinetics of measles antibody by hemagglutination inhibition assay in children in south-west and north-central Nigeria

SummaryObjectivesWe investigated the antibody level of children against wild measles virus in view of recurrent measles epidemics, in order to provide information on immunization status for health policies and for the global measles mortality reduction initiative.MethodsTwo hundred and seventy-three children between the ages of 10 months and 13 years were recruited for this study from three hospital facilities in south-west and north-central Nigeria. Serum samples were collected from February to July 2009, and laboratory examination commenced in August of the same year. Measles hemagglutinin (HA) antigen was prepared by culturing the measles vaccine virus strain (Edmonston-Zagreb) in a vero/hSLAM cell line. Serum samples were treated to get rid of potentiating factors, non-specific inhibitors, and agglutinins before the HA/hemagglutination inhibition (HI) procedure.ResultsOut of the 175 children vaccinated in Ibadan, 60 (34.3%) had an antibody level not sufficient to protect against measles infection. Likewise, 12 (25.0%) vaccinated children from Ilorin had an antibody level not sufficient to protect against measles infection. There was no significant difference in the level of protection between the children in Ibadan and Ilorin (p > 0.05). The geometric mean titer (GMT) was 53.83 for males and 48.64 for females. There was no significant difference between the GMTs of females and males in both locations (p > 0.05). Also, no significant difference was observed in the GMTs of children in both locations (p > 0.05).ConclusionsOf the vaccinated children, 157 (57.5%) developed protective measles virus HI antibody, which is not enough to maintain protective herd immunity. Hence there is a need for catch-up and follow-up vaccination programs, especially in rural areas and places with difficult terrains, in order to reduce measles mortality.