Immunity Against Measles in Urban Refugee Children, Adolescents, and Young Adults in Eastleigh, Kenya

Background: Kenya has made progress towards the elimination of measles through routine and supplementary immunisation activities; however, sporadic outbreaks still occur. Studies on measles seroprevalence in Kenya are few and extensive analysis of refugee and migrant populations’ immunity against measles is lacking. This cross-sectional study aimed at assessing the presence of immunity against measles in children, adolescents and young adults living in the high urban refugee area of Eastleigh Nairobi, Kenya. Method: A total of 384 samples serum samples were collected from consenting respondents and tested for measles IgG antibodies. Syncytium Inhibition Assay, a neutralisation assay was used to determine functionality. The establishment of herd immunity was calculated using the Plans- Rubio formulae. Results: Seropositive rate for all respondents were 84.38%, while equivocal and negative were 4.95% and 10.68%, respectively. None of the factors analysed was a significant predictor of positive measles antibodies. 87.76% of the total sera were neutralising, while 12.23 % were negative. There was a significant correlation between the neutralisation titres and ELISA values. Conclusion: This study highlights age-specific measles immunity gaps in an urban refugee population. Although measles antibodies are present in all age groups, none has established herd immunity. In order to avert outbreaks in the study population, it is necessary to direct immunisation interventions to increase the measles antibody prevalence to recommended levels.