Pneumococcal infections at Hajj: current knowledge gaps.

Hajj attendance increases the risk of respiratory infections including pneumonia. Streptococcus pneumoniae is a frequently identified pathogen, found in about 10% of respiratory tract samples of symptomatic Hajj pilgrims; and at least 20% of these isolates are penicillin resistant. However, the burden of pneumococcal disease at Hajj is not precisely defined at serotypic level, and it is postulated that due to intense mixing of pilgrims the distribution of pneumococcal serotypes at Hajj could be different from pilgrims' country of origin or of Saudi Arabia. In Saudi Arabia, the most prevalent pneumococcal serotypes are 23F, 6B, 19F, 18C, 4, 14, and 19A, and 90% of the serotypes are covered by 13-valent pneumococcal conjugate vaccine (PCV-13) as well as 23-valent pneumococcal polysaccharide vaccine (PPV-23). However, due to lack of Hajj-specific data, the Saudi Arabian Ministry of Health has not yet recommended pneumococcal vaccine for pilgrims, and the immunisation recommendation and uptake vary greatly across countries. As at least one third of Hajj pilgrims are 'at risk' of pneumococcal disease either by virtue of age or pre-existing medical conditions, consideration should be given to vaccinating high risk pilgrims against pneumococcal disease. Other preventive measures such as smoking cessation, pollution reduction and vaccinations against influenza and pertussis should also be considered. Precisely defining the epidemiology of pneumococcal disease to identify an optimum vaccination schedule for Hajj pilgrims is a current research priority.