Epidemiology of Rubella in Nigeria, 2013-2017

  • Vaccine preventable diseases
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Rubella is a mild illness in children but may result in congenital rubella syndrome (CRS) when it affects pregnant women. Nigeria tests for rubella as part of measles case-based surveillance but is yet to commence CRS surveil- lance or introduce a rubella vaccine into the national immunization programme. We described the epidemiology of rubella cases from measles case-based surveillance data and analysed risk factors for rubella IgM positivity.
We extracted data of all rubella positive cases from 2013 to 2017 from the national routine measles case-based surveillance system. The database includes patients with suspected measles, according to the WHO clinical case definition. Based on an algorithm, samples are tested for measles IgM; samples that test negative or indeterminate for measles IgM are tested for rubella-specific IgM. We described the data and calculated odds ratios (OR) with 95% confidence intervals (CI) to determine factors associated with rubella IgM positivity.
Of the 17,549 measles IgM-negative samples tested, 1,548 (8.8%) tested positive for rubella IgM. The median age of the rubella positive patients was 4 years (range: 1 month to 60 years). Sixty (3.9%) of the rubella-positive cases were women of child-bearing age (WCBA). Cases occurred predominantly during the dry season with 915 (60%) occurring between December and March. Patients >5 years of age (OR= 1.6; 95% CI: 1.4-1.7), those from the southern region of the country (OR= 1.7; 95% CI: 1.5-2.0) and those who had received two or more doses of measles vaccines (OR= 1.3; 95% CI: 1.2-1.5) were more likely to test positive for rubella. There was no relationship between settlement type (urban /rural) (OR=1.1; 95% CI: 1.0-1.2) and sex (OR= 1.0; 95% CI: 0.9-1.1) and rubella positivity.
The on-going rubella transmission in Nigeria affecting WCBA portends a high risk of CRS. We have finalized plans to establish surveillance for CRS. We recommend introduction of a rubella containing vaccine into the national immunisation schedule.

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