The Epidemiology of Rubella in Lesotho before the Introduction of a Rubella Containing Vaccine: A Review of Measles Case-based Surveillance, 2012-2016

Aim: The aim of the study was to determine the burden and epidemiology of rubella infection in Lesotho before the introduction of a rubella-containing vaccine. It was also to assess the performance of the measles case-based surveillance system in Lesotho.

Study Design: Retrospective cross-sectional descriptive study.

Place and Duration of Study: The study was done in Lesotho from February to March 2019 based on the 2012 to 2016 data.

Methods: There was a review of the measles case-based surveillance data with a total of 1587 suspected cases reported during the study period. Samples were collected from suspected measles cases and tested for measles. Those samples that tested negative for measles were subsequently tested for rubella IgM at the National Reference Laboratory. The serum samples were analysed for rubella IgM using commercial enzyme-linked immunosorbent assay (ELISA) kits SERION and EUROIMMUN.

Results: There were 2 measles IgM and 748 rubella IgM positive cases confirmed. The rubella IgM positive cases accounted for 48% of the samples tested for rubella infection. There were also several rubella outbreaks during the study period. The Lesotho surveillance system met the two principal surveillance performance indicators for each year during the period of the study.

Conclusion: This study showed that there was high level of rubella sero-positivity with several outbreaks of rubella infections during the study period. Rubella infection was predominantly seen in those aged between 5 and <13 years of age. This justified the introduction of a rubella containing vaccine in Lesotho in 2017. Although the two principal surveillance performance indicators (non-measles febrile rash illness rates and the percentage of districts that reported at least one case of measles with blood specimen per year) were met during the period under review, there were districts that performed poorly. This study revealed the need for strengthening of rubella-containing vaccine component of routine immunization to lower the impact of rubella infection in Lesotho. A detailed district level review to identify and address the causes of poor performance in some districts is recommended. There is also a need to identify the current challenges and evaluate the impact of the recently introduced rubella-containing vaccine on rubella infection in Lesotho.