EPIDEMIOLOGICAL CHARACTERISTICS, VACCINATION COVERAGE AND FACTORS ASSOCIATED WITH MEASLES INFECTION IN SIERRA LEONE FROM 2017 TO 2021; CASE BASED SURVEILLANCE DATA

Abstract

Despite the availability of safe and effective vaccines, measles outbreaks continue to occur in Sierra Leone. There is still limited information on the epidemiological pattern and vaccination coverage of measles in the country. This research aims at describing the epidemiological characteristics, vaccination coverage and identify factors associated with measles infection. We employed a cross-sectional study to analyze measles secondary data generated from 2017 to 2021. We extracted data on measles-containing vaccine (MCV) coverage and dropout. We analyzed the spatial distribution of measles cases by person, place, and time, calculated incidence, MCV coverage, and drop-out rate. Statistical analyses were performed using Epi Info 7. A multiple logistic regression model was used to calculate the adjusted odds ratio (aOR) with a 95% Confidence Interval (CI) to assess factors associated with measles infection. Results showed that a total of 1,305 suspected measles cases were reported. Of the total, 1,133 were confirmed as measles cases, of which 270 (24%) were IgM positive and 863 (76%) were Epi-linked or clinically confirmed. The mean age was 3.9-year 4.5 SD. Of the total confirmed measles cases, 575 (51%) were between 1 to 4 years, females accounted for 580 (51%), and 699 (62%) were not vaccinated. Non-border districts accounted for 54% (614) measles cases. The national measles incidence per 100,000 population was 203.8 in 2017 and 26.9 in 2021. The MCV1 national coverage ranged from 243,525/269,981 (90%) in 2017 to 238,505/307,022 78% in 2021, with the highest coverage in 2019, which is 266,684/284,452 (94%) and the lowest coverage in 2021 (78%). Children less than 5years old (aOR 2.28, 95% CI: 1.56 to 3.33), not vaccinated (aOR 3.42, 95% CI: 2.41 to 4.86), and border districts (aOR 0.37, 95% CI: 0.26 to 0.53) are factors associated with measles infection. We observed a high measles incidence rate in 2017. The country did not meet its national target for MCV-1 and MCV-2 in all years under study Children under five, those living in border districts, and unvaccinated individuals were more likely to contract measles. We recommend strengthening routing and supplementary immunization campaigns, prioritizing outreach services, and heightening social mobilization activities.

Keywords: Measles, Measles-Containing-Vaccine (MCV), factors of measles infection, Sierra Leone.