Pneumococcal Pneumonia

The Streptococcus pneumoniae bacterium (often called pneumococcus) can cause a variety of diseases, from severe, potentially life-threatening pneumonia, meningitis, and bacteremia to common but less severe otitis media (an ear infection), sinusitis, and bronchitis. These "pneumococcal" diseases, which preferentially attack young children, older adults, and people with immunosuppressive conditions, such as HIV, present significant public health problems.

WHO estimated in 2005 that 1.6 million people die of pneumococcal disease annually, with 63 percent of these deaths occurring in children under age five, and the vast majority occurring in developing countries.[19] In the United States, pneumonia and influenza combined represent the leading infectious cause of mortality in children one to four years old, and the eighth leading cause of death overall.[20] Otitis media is the most common cause of sick visits in preschool-age children in the United States, with 24.5 million clinic visits and $2 to 5.3 billion in annual treatment costs. By three years old, 83 percent of U.S. children will have experienced at least one episode of otitis media.[21] Otitis media is the most common reason for antibiotic prescriptions among U.S. children and thus contributes significantly to growing antibiotic resistance.

Designing an effective vaccine to immunize patients against pneumococcus is challenging, because more than 90 different "serotypes" of the bacterium have been identified. Each of these microorganisms is unique, with slightly different proteins and polysaccharides (complex sugars) on their surface.[22]

When the human body produces antibodies to a single bacterium, these typically provide protection against a single serotype. (This is the reason that the same patient may contract multiple ear infections.) Therefore, the recent strategy in pneumococcal vaccine design has been to include in the formulation polysaccharides from multiple serotypes, with a focus on those that most commonly cause severe, invasive disease, to build up broader protection through vaccination.

In 2000, the first of these pneumococcal conjugate vaccines, PVC-7, was released. This vaccine included seven serotypes covering 65 to 80 percent of bacteria associated with invasive pneumococcal disease among young children in Western Hemisphere industrial countries.[23] In the United States, this vaccine was almost immediately recommended for all children under two years old,[24] and it has already enjoyed dramatic success. In the eight years since the introduction of the vaccine, there has been a 69 percent to 91 percent decrease in the rate of invasive pneumococcal disease.[25, 26] Although the decrease has been most dramatic in young children, the vaccine's target group, significant declines have been seen in older children, adults, and the elderly,[27-30] suggesting that the vaccine induces herd immunity. Also, dramatic reductions in otitis media and severe cases of otitis requiring tympanostomy tubes have been reported.[31-34]