Throughout the year, Muslims from all over the world visit the holy city of Makkah (Mecca), Saudi Arabia, for Umra, a minor Islamic pilgrimage. Umra visits are heaviest during Ramadan, the Muslim fasting month, when the population of Makkah increases fivefold. Because of the danger of meningococcal disease (MCD) in this situation, Makkah routinely vaccinates its residents against MCD. During Ramadan (March-April) of 1992, surveillance began detecting increasing numbers of MCD in Makkah. A mass vaccination campaign using meningococcal bivalent (AC) polysaccharide vaccine was begun. We began an epidemiologic investigation to find out the associated risk factors for MCD and to investigate and monitor the effect of mass vaccination.
Methodology
We reviewed medical records of all MCD cases in six hospitals in Makkah and interviewed patients. High throat swabs were taken from 42 apparently healthy subjects visiting the Haraam, the holy mosque in Makkah, and 67 patients visiting outpatient clinics in two hospitals. We selected 114 controls matched by residential area and sex and interviewed them to find out why they had not been vaccinated.
Results
We identified 102 bacteriologically confirmed cases (CC) and 80 suspected cases (SC) of MCD. Neisseria meningitidis was identified as Group A, III-1 clone. The ratio of male to female cases was 2.9:1. All age groups of males were affected. There was only one case among females aged 10-30; 50% of the adult female cases were 55 or older. SC showed a similar pattern. The case-fatality ratio (CFR) was 13.7% among CC. Pakistanis, who comprised about one-third of the CC, had a CFR of 26%. Fifty-nine percent of CC were religious visitors. CC in residents were most common in persons living near the Haram, where the carriage rate was 86%. An abrupt drop, from a mean of 15 CC per week to two CC per week (only in visitors), coincided with vaccinating 600,000 persons over two weeks. Makkah residents who had never been vaccinated against MCD were more likely to have had MCD (OR=13, 95% CI: 5.6-29). The main reason for not being vaccinated as stated by both cases 71%) and controls 45%) was not knowing about the disease.
Conclusion
Mass vaccination promptly halted the outbreak of MCD. The age and sex differences probably relate to the difference in exposure to crowded conditions. Health education should illuminate the seriousness of the disease and the importance of vaccination.