Two types of pneumococcal vaccines are approved for use in the United States:
●Pneumococcal polysaccharide vaccine (PPSV; Pneumovax) was first marketed in the 1970s as a vaccine that contained capsular polysaccharides from 14 pneumococcal serotypes that commonly caused disease. In 1983, this vaccine was augmented to include capsular polysaccharides from the 23 most commonly infecting pneumococcal serotypes and is marketed as Pneumovax 23 (PPSV23) (table 2). At present, PPSV23 contains capsular polysaccharides from pneumococci that cause about 60 percent of all pneumococcal infection in adults . PPSV is used in selected adults and children ≥2 years of age but not in infants or toddlers <2 years of age since polysaccharide antigens are poorly immunogenic in this age group.
●Pneumococcal conjugate vaccine (PCV; Prevnar) was initially marketed in the United States in 2000 as PCV7, a vaccine containing polysaccharides from the seven pneumococcal serotypes that caused most pneumococcal disease in young children. The polysaccharides are covalently linked to a nontoxic protein that is nearly identical to diphtheria toxin, which renders the polysaccharides antigenic in infants and toddlers. Because PCV7 is an excellent immunogen in infants and toddlers, it was adopted in the United States for universal use in this age group in 2000. In 2010, PCV7 was replaced by PCV13, a vaccine that has added serotypes commonly implicated in disease to those contained in PCV7. Since 2010, PCV13 has been recommended for infants and children in place of PCV7. It is also recommended for selected adults. PCVs with different numbers of serotypes are produced in other parts of the world (table 2).
Because PCV stimulates mucosal antibody, it greatly suppresses nasal carriage of S. pneumoniae due to vaccine serotypes. Not surprisingly, therefore, widespread use of PCV7 has reduced spread of pneumococci from small children, the usual reservoir of pneumococcal carriage, to unvaccinated older children and adults, an effect that is called an indirect (or “herd”) effect. In the pre-PCV era, about 65 to 70 percent of pneumococcal pneumonia in adults was caused by strains included in PCV7. By 2008 in the United States, disease due to these types had nearly disappeared from the adult population, largely as a result of this indirect effect. The same kind of decline in infection of adults due to serotypes in PCV13 has begun to be apparent.
In one study, it was estimated that, in 2013, PCV13 stimulated antibody to serotypes that caused 28 to 42 percent of invasive pneumococcal disease in adults in the United States . In the United States and other countries with universal PCV immunization programs, this percentage is declining as a result of indirect immunity, with a three- to four-year lag period when compared to the effect on invasive pneumococcal disease in vaccinated children .
The indications for use of PPSV23 and PCV13 in adults are presented below. (See ‘Indications’ below.)
The use of pneumococcal vaccines in infants and children is discussed in detail separately. (See “Pneumococcal (Streptococcus pneumoniae) conjugate vaccines in children” and “Pneumococcal (Streptococcus pneumoniae) polysaccharide vaccines in children”.)