Since adoption of Measles elimination goals in 1996, Measles cases have decreased significantly barring two nation-wide outbreaks in 2004 and 2007. In early 2011, an unexpectedly large number of Measles cases were reported from the Buraidah sector of Qassim region and, at the request of local health authorities, a team from the Saudi Field Epidemiology Training Program (FETP) investigated the outbreak to describe the outbreak and identify risk factors for its occurrence.
Methodology
A descriptive study was conducted to collect information about all the cases which occurred in Buraidah sector from 1st January to 20th May, 2011. It was followed by a case-control study using a structured interview schedule and a case-to-control ratio of 1:2, while matching for age-group, gender and place of residence.
Results
From 1st January to 20th May 2011, 40 confirmed Measles cases were reported in the Buraidah sector of Qassim region (an attack rate of 13/100,000 population). 60% of the confirmed cases were females and 40% of cases were older than 18 years. Twelve cases were among a small nomadic group. One case and 55 (75.3%) controls had received at least one dose of measles vaccine (OR 0.01; 95% CI 0.00 - 0.07), with a vaccine efficacy of 99.1%. Disease status was directly associated with a history of contact with a known Measles case (OR 3.23; 95% CI 1.26 - 8.38) and inversely associated with travel within the region (OR 0.26; 95% CI 0.09 - 0.71). But no statistically significant relationship was observed with history of travel out of Al-Qasseem region and visit to a health facility.
Conclusion
Main factors responsible for this measles outbreak in Buraidah were poor vaccination in select nomadic group, weaknesses in routine immunization and waning immunity in older population.