Journal of Microbiology Research 2013, 3(6): 266-273 DOI: 10.5923/j.microbiology.20130306.12 Low Level of Pre-Vaccination Measles Antibody among Infants Receiving Measles Immunization in Ilorin, Kwara State, Nigeria Fowotade A. 1 , Okonko I. O. 2,* , Nwabuisi C. 3 , Fadeyi A. 3 , Bakare R. A. 1 , Adu F. D. 4 1 Department of Medical Microbiology & Parasitology, University College Hospital, Ibadan, Nigeria 2 Medical Microbiology Unit, Department of Microbiology, University of Port Harcourt, P.M.B. 5323, Choba, East-West Road, Port Harcourt, Nigeria 3 Department of Medical Microbiology & Parasitology, University of Ilorin Teaching Hospital, Ilorin, Nigeria 4 Department of Virology, College of Medicine, University of Ibadan, Ibadan, Nigeria Abstract This study was designed to assess the low levels of pre-vaccination measles antibody among infants receiving measles immunization in Ilorin, Kwara State, Nigeria. Pre-vaccination blood samples were obtained from 400 infants brought to the EPI Clinic of the University of Ilorin Teaching Hospital, Ilorin, Nigeria. Blood samples were collected by finger puncture onto ROPACO (Rochester, USA) rectangular filter paper measuring 7 cm by 10 cm. Other information like name, age, sex, date of vaccination was also recorded on the filter paper. The filter papers were dried at ambient temperature and stored in plastic bags at -20℃ until ready for serum extraction. Specimens were analyzed for measles antibody using Hemagglutination Inhibition technique. Data generated were subjected to Chi square statistical test to establish association between categorical variables with dichotomous outcomes. Of all the 400 infants screened for pre-vaccination measles antibodies, 29(7.2%) had protective antibody titer while 156 (39.0%) had low titer since ≥40 HI titer is the study threshold of protection against measles while 215(53.8%) had no detectable measles antibody titer (<1:10). Thirty-one (8.0%) of the infants had measles prior to vaccination. Previous history of measles was significant associated (P=0.0005, X2 = 34.507) with the level of pre-vaccination measles virus antibody. There was no significant difference (p=0.723) in the level of measles virus antibody among the exclusively breastfed infants and those that were not exclusively breast fed. Age (p=0.839) and sex (p=0.1999) were not significantly associated with the level of measles virus antibody. The distribution of this antibody levels appeared stable with no significant difference between age groups, sex and breast feeding pattern. Only the previous history of measles showed statistical association with measles virus antibody proportion. In conclusion, a larger proportion (53.8%) of the children had no detectable anti-measles virus antibody while 39.0% had low (non-protective) titer; these put both groups at risk of developing measles given the endemic nature of Nigeria. Therefore, re-evaluation of 9 months as the age for measles vaccination in Nigeria vis-à-vis 92.8% with <40 HI titer is highly recommended. Keywords Hemagglutination Inhibition, Pre-vaccination, Measles Antibody, Measles Immunization, Vaccination 1. Introduction Measles infection occurs worldwide but it is epidemic in developing countries where severe morbidity and high mortality are associated with underlying malnutrition, poverty, and indiscriminate vaccination services[1- 3]. The optimum age for measles vaccination varies from country to country thus a standardized vaccination schedule is controversial. While the increase in measles vaccination coverage has produced significant changes in the epidemiology of infection in developing countries, measles * Corresponding author: mac2finney@yahoo.com (Okonko I. O.) Published online at http://journal.sapub.org/microbiology Copyright © 2013 Scientific & Academic Publishing. All Rights Reserved morbidity and mortality represents an important public health problem, with a significant number of infections occurring earlier than the 9 months[4]. Several researchers have reported the occurrence of measles in infants less than 9 months old[5-6] . Some studies have attributed the occurrence of measles among infants less than 9 months to low affinity maternal measles antibody which consequently increases the vulnerability of these infants to circulating wild measles strains[7-8]. Oyedele et al.[6] revealed that while 58% of Nigerian children lost their protective maternal antibody by the age of 4 months only 3% had enough antibodies to protect them between the ages of 6-9 months. Nevertheless, in West Africa, measles vaccine is given at 9 months of age which based on an early serological study in Kenya is thought to be the optimal age for protection against measles in endemic areas where maternally derived antibody