Streptococcus pneumoniae serotypes/serogroups causing invasive disease in riyadh, saudi arabia: extent of coverage by pneumococcal vaccines

Streptococcus pneumoniae (pneumococcus) is a leading cause of morbidity and mortality worldwide.1 It causes a wide variety of diseases ranging from severe invasive infections such as bacteremia and meningitis to relatively benign infections such as otitis media and sinusitis. e pneumococcus is the commonest cause of community-acquired pneumonia and otitis media. It is estimated that pneumococcal infections lead to the death of over one million children below 5 years of age annually.2 Efforts to prevent pneumococcal infections by immunization with the 23-valent polysaccharide vaccine have been of limited success due to its poor immunogenicity in children below 2 years of age.3 e recently produced protein-polysaccharide conjugate pneumococcal vaccines have good immunogenicity even in infants. e major drawback of this class of vaccines is that due to technical and logistic reasons, only a limited number of strains can be formulated in the vaccine. e prevalent pneumococcal serotypes responsible for invasive diseases vary between developing and developed countries.3,4 us, determination of the prevalent pneumococcal serotypes causing invasive disease in each region is crucial for the formulation of vaccines suitable for each region. e currently available 7-valent conjugated vaccine has proven efficacy in preventing invasive pneumococcal disease in infants;5 however, the serotypes included in the vaccine are those responsible for the majority of invasive infections in developed countries and therefore may not offer adequate coverage in most developing countrie