Sustained outbreak of W135 meningococcal disease in east London, UK

Abstract

S J M Hahné and colleagues1Hahné SJM Gray SJ Aguilera J-F et al.W135 meningococcal disease in England and Wales associated with Hajj 2000 and 2001.Lancet. 2002; 359: 582-583Summary Full Text Full Text PDF PubMed Scopus (88) Google Scholar report a high attack rate and associated high fatality rate of Hajj associated meningococcal disease in pilgrims and their contacts, caused by a previously rare serogroup W135 strain. They call for better implementation of current vaccine-based control policies. However, although quadrivalent meningococcal vaccine may protect the pilgrims, there is still no consensus on how best to protect contacts of pilgrims and to prevent dissemination of the strain. Hahne and colleagues note that the ratio of infected contacts to infected pilgrims did not rise in 2001, and speculate that this finding may be consistent with an effect of the vaccine on carriage. They conclude that development of appropriate publichealth policies is hampered by the absence of robust data on the effect of the quadrivalent vaccine on carriage. We did a prospective study on meningococcal carriage rates in Hajj pilgrims before and after the Hajj 2001.2Wilder-Smith A, Barkham TMS, Earnest A, Paton NI. Acquisition of meningococcal carriage in Hajj pilgrims and transmission to household contacts. BMJ (in press).Google Scholar All pilgrims had received the quadrivalent vaccine. The carriage rates before and after the Hajj, were 0·5% and 17·0%, respectively. Of the meningococcal isolates in Hajj returnees, 79% were identified as serogroup W135. We cannot rule out an effect of the vaccine on carriage because all were vaccinated. Since quadrivalent vaccine is now a Hajj visa requirement, it is unlikely that such a comparative study can be done. However, even if polysaccharide vaccines can temporarily reduce carriage,3Stroffolini T Angelini L Galanti I Occhionero M Congui ME Mastrantonio P The effect of meningococcal group A and C polysaccharide vaccine on nasopharyngeal carrier state.Microbiologica. 1990; 13: 225-229PubMed Google Scholar such an effect is probably small, and certainly not sufficient to prevent carriage. Future vaccine developments should focus on conjugate quadrivalent vaccines, which may have a better effect on the reduction of carriage than the current polysaccharide quadrivalent vaccine.4Maiden MC Spratt BG Meningococcal conjugate vaccines: new opportunities and new challenges.Lancet. 1999; 354: 615-616Summary Full Text Full Text PDF PubMed Scopus (102) Google Scholar Furthermore, transmission of the W135 strain from returning pilgrims to their household contacts was 13·0%.2Wilder-Smith A, Barkham TMS, Earnest A, Paton NI. Acquisition of meningococcal carriage in Hajj pilgrims and transmission to household contacts. BMJ (in press).Google Scholar Therefore, although vaccination might protect the pilgrims from invasive disease, returning pilgrims represent a sizeable reservoir of a virulent and highly transmissible W135 clone, which places their unvaccinated family contacts (and possibly the community at large) at risk of invasive disease. In addition to the better coverage with quadrivalent vaccination for all pilgrims proposed by Hahné and colleagues, public-health strategies need to be implemented urgently to prevent introduction of this clone into the pilgrim's countries of origin. One dose of 500 mg ciprofloxacin can eradicate nasopharyngeal carriage of meningococci in more than 90% of carriers with few side-effects.5Gaunt PN Lambert BE Single dose ciprofloxacin for the eradication of pharyngeal.Neisseria meningitidis. J Antimicrob Chemother. 1988; 21: 489-496Crossref PubMed Scopus (54) Google Scholar Our results would support a policy of administering antibiotics to returning pilgrims to eradicate carriage and thereby protect household contacts. Identification of populations of incoming pilgrims carrying W135 is needed for targeted carriage eradication to prevent the introduction and dissemination of this clone during the pilgrimage.