Factors associated with detection of measles-specific immunoglobulin M (IgM-positive) in Cte dIvoire from 2015 to 2019: A nested case-control study from a measles national surveillance programme

Measles outbreaks are regularly reported in Côte d’Ivoire districts although on-going measles vaccination coverage has increased. The objective was to identify the factors associated with measles IgM-positive in a population with suspected measles. A case-control study nested in the national surveillance of 9337 registered measles suspected cases from 2015 to 2019 in Côte d'Ivoire was conducted for identification of factors associated with laboratory-confirmed case-based measles. The independent factors associated with detection of IgM in blood were determined from logistic regression. Among suspected measles cases, 88.84% had blood samples taken to test for measles IgM antibody. The proportion of IgM-positivity was 10.03% among the 8295 blood samples tested at the measles reference laboratory. The median age of the population tested was four years (y) with an interquartile range (IQR) [1.5-9 years]. The majority of IgM-positive subjects (71.28%) were aged from 1 to 15 years. Of the IgM-positive subjects, 52.05% had an unknown vaccination status. The independent factors associated with the presence of IgM were: Unvaccinated status against measles (adjusted odds-ratio [aOR]=2.82, 95% confidence interval (CI) 2.19 to 3.64), increasing age (aOR(95% CI): 1.37(1.06 to 1.78), 1.54(1.18 to 2.00), 1.56(1.14 to 2.12) for age groups 1-5 years, 5 to 15 years, 15 years +, respectively compared with the age group 0 to 1 year, and health regions of residence located in the west of Côte d’Ivoire aOR ranged between 1.68 (Haut Sassandra) and 2.87 (Marahoue). Interventions considering factors associated with measles IgM-positive will help to control the spread of measles in Cote d’Ivoire. Key word: Measles-specific M-immunoglobulin, measles, vaccination, logistic regression, surveillance programme, Côte d’Ivoire.