From January 1 to March 12, 1997 an unusual increase in measles cases (35) was reported from Najran, a rural region in southwest Saudi Arabia. From 1992 through 1996 only 69 cases had been reported from the Najran region. An epidemiologic investigation was requested.
Methodology
We sent a new circular to all government and private health sectors requesting that they report all measles cases within 24 hours. We defined an outbreak-associated case of measles as a febrile illness with a generalized maculopapular rash for 3 days, and cough, coryza or conjunctivitis occurring between December 25, 1996 - March 12, 1997 in Najran region. A case-control study was conducted among families with measles cases patients. Five control persons were selected for case-patients < 13 years old and > 13 years old respectively. Controls were group matched by neighborhoods.
Results
The first measles case-patient was an unvaccinated 23 year old male who reported exposure to a measles patient while in a neighboring region. Following this importation, 3 separate chains of transmission were identified. Community contact was identified in schools (6 cases), medical clinics (6 cases) and football matches (1 case). Most (74%) measles case-patients were over the age of coverage by universal vaccination (13) and ranged up to 41 years of age. However a rubella control program using MMR in schools covered females from 13 to 26 years. In this group only 17% of cases were in females. Among persons > 13 years 3.8% of cases and 30% of controls had prior measles vaccination (vaccine effectiveness of 91%; 95% CI=26%-99%). High vaccination coverage (93% in control children) in children 13 years or younger prevented computation of vaccine effectiveness in this age group.
Conclusion
Males over the age of 13 years born before the year of universal measles vaccination (1983) helped maintain a chain of measles transmission in Najran. Vaccination of adolescent and young adults may be needed to prevent continuing transmission of measles in rural Saudi Arabia.