Impact of the Hajj on pneumococcal carriage and the effect of various pneumococcal vaccines

International audienceBackground: The Islamic Hajj pilgrimage is the largest annual mass gathering in the world. The overcrowding of people promotes the acquisition, spread and transmission of respiratory pathogens, including Streptococcus pneumoniae. Methods: We conducted a methodological review according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. The objective was to summarize the available data regarding the prevalence of pneumococcal carriage among Hajj pilgrims and about carriage acquisition and circulation of S. pneumoniae among pilgrims before and after participating in the Hajj according to their vaccination status. Results: Eight articles met eligibility criteria for pneumococcal carriage and impact of pneumococcal vaccination on carriage. Seven of them showed a significant increase in nasopharyngeal carriage of pneumococci following the pilgrimage, with acquisition rates ranging from 18 to 36%. Serotypes 3, 19F and 34 are the most common. A significant increase in antibiotic resistant strains was observed following participation in the Hajj. A lower prevalence was found in pilgrims treated with antibiotics, those who used a hand sanitizer, or those who washed their hands more frequently than usual. An increased carriage of pneumococcal serotypes included in pneumococcal vaccines (10-valent pneumococcal conjugate vaccine (PCV10), 13-valent pneumococcal conjugate vaccine (PCV13), 23-valent pneumococcal polysaccharide vaccine (PPV23)) was observed following participation in the Hajj. To date, no study has shown a significant reduction in pneumococcal carriage among pilgrims after vaccination with PPV23 or PCV. In fact, no significant difference was currently observed in the prevalence ratio of pneumococcal carriage between vaccinated and unvaccinated pilgrims. Conclusion: The studies analyzed in this review showed an increased carriage of pneumococcus in post-Hajj pilgrims compared to pre-Hajj pilgrims, including vaccine serotypes. Further studies are needed to investigate the possible relationships between carriage, disease and vaccine in pilgrims. (C) 2018 Elsevier Ltd. All rights reserved