Meningococcal serogroup A, C, W, and Y serum bactericidal antibody profiles in Hajj pilgrims.

Background: The religious seasons of Hajj and Umra in the Kingdom of Saudi Arabia (KSA) have historically been associated with epidemics of meningococcal disease. Due to the effective preventive measures taken in recent years, including vaccination, no meningococcal outbreaks have been reported during Hajj or were Hajj-associated. However, little is known about the immunological profile of pilgrims. The aim of this study was to assess the immunological profile of pilgrims on arrival in KSA against the four meningococcal serogroups, A, C, W, and Y, contained within the quadrivalent vaccine.

Methods: Following consent, socio-demographic factors and health-related information was collected from pilgrims arriving at King Abdul Aziz International Airport and a blood sample taken. Antibodies were quantified by serum bactericidal antibody assay using baby rabbit complement (rSBA) against the four meningococcal serogroups, A, C, W, and Y.

Results: Serum samples were collected from 796 pilgrims; rSBA results were obtained for all four serogroups for 741 of these samples. A total of 48 (6.5%) Hajjis had previously attended Hajj, ranging from 1 to 14 times (median 2 times); 98.2% had received meningococcal quadrivalent vaccine in the last 3 years. Of the 13 who had not, all originated from Bangladesh, with four reporting no previous meningococcal vaccination and nine reporting having received the vaccination more than 3 years ago. For serogroup A, only one pilgrim from Indonesia had an rSBA titre <8. For serogroups C, W, and Y, the percentages of pilgrims with rSBA titres <8 were 9.9%, 17.4%, and 9.4%, respectively. Of note was the high prevalence of non-complement-mediated lysis in pilgrims originating from Nigeria (28/47; 59.6%) and Afghanistan (21/47; 44.7%), but not the other countries. This may be a reflection of the type and pattern of antibiotic usage among these communities.

Conclusion: The vast majority of pilgrims are vaccinated and protected against meningococcal serogroups A, C, W, and Y.