Pneumococcus

Streptococcus pneumoniae is a common cause of community-acquired pneumonia, bacteremia, and meningitis in all groups beyond the newborn period throughout the world. At least 98 different serotypes of the pathogen have been identified based on characteristics of the polysaccharide capsule. Ten of these serotypes are responsible for causing more than 60% of invasive infections. Vaccines developed using serotype-specific polysaccharide immunogens have been used to immunize children ≥2 yrs of age and adults at risk for several decades. Polysaccharide vaccines are effective but have several inherent limitations that include lack of immunogenicity in children <2 yrs of age and rapidly waning immunity over 5 years in older children and adults that is not boosted with repeat doses. These limitations were overcome by novel vaccine technology that uses the same polysaccharide immunogens linked to a carrier protein, forming a conjugate vaccine. Protein conjugate vaccines are capable of inducing robust immune responses, with the development of immune memory, in children as young as 6 weeks of age. Conjugate pneumococcal vaccines have been added to pediatric vaccine schedules of more than 140 nations worldwide resulting in dramatic declines in disease morbidity and mortality everywhere they have been introduced.