Epidemiological Analysis of Notified Measles Cases and Review of Surveillance System During an Outbreak in Tabuk, Saudi Arabia

PURPOSE: In response to a measles outbreak occurred in Tabuk, Saudi Arabia, we conducted a case-based active-surveillance, and analyzed all surveillance data to identify the epidemiology of notified measles cases and to review the surveillance system. METHODS: Suspected and confirmed measles cases were defined according to World Health Organization (WHO) guidelines. Household-based investigation was conducted for all suspected cases using standard measles notification form. Enzyme-linked immunosorbent assay was carried out on serum samples collected from all suspected cases to detect measles specific immunoglobulin M (IgM) antibodies. Surveillance system was assessed by preselected performance indicators consistent with WHO guidelines. Logistic regression was used to calculate crude and adjusted odds ratios from the surveillance data. RESULTS: Of 242 suspected measles cases notified between 3rd and 48th calendar weeks of the study-year, laboratory result was IgM-positive for 46% cases, IgM-negative for 49% cases, and unknown for 5% cases. Suspected and confirmed cases separately showed urban-predominance (> 77%), male-majority (> 51%), and high-proportion among Saudis (> 92%). The highest proportion (93%) of suspected cases that received "at least one dose" of measles-containing vaccine (MCV) was found among those aged 12-17 years, whereas the lowest proportion (17%) was observed among the adult individuals (>= 18 years). Elderly (>= 18 years) individuals were significantly less likely to be vaccinated than younger (1-5 years) children (adjusted odds ratio [OR] = 15.92, 95% confidence interval [CI] = 4.82-52.56). The vaccine failure rate for "at least one dose" of MCV was 35%. The individuals vaccinated with "at least one-dose" of MCV were at 3.6 times lower risk of contracting measles than the nonvaccinated group (adjusted OR = 3.6, 95% CI = 1.55-8.38). Of five surveillance performance indicators, three were found as per WHO target. CONCLUSIONS: More efforts are essential to prevent future outbreaks and to reach the goal of measles elimination in the country. Ann Epidemiol 2011;21:262-271. (C) 2011 Elsevier Inc. All rights reserved.