Introduction: Infant immunization programs using pneumococcal conjugate vaccines (PCVs) have reduced the rates of pneumococcal disease through direct vaccine-induced protection in vaccinated children and through indirect protection in non-vaccinated children and adults.
Areas covered: This review summarizes current evidence on the indirect protection of adults conferred by pediatric pneumococcal vaccination, including the impact on invasive pneumococcal disease (IPD) incidence and mortality, pneumonia admissions, and nasopharyngeal carriage prevalence. Factors affecting indirect protection against IPD are also discussed.
Expert opinion: Pediatric immunization with PCVs has substantially decreased vaccine-serotype IPD and pneumonia through indirect protection in both older (≥65 years of age) and younger adults, including those with underlying medical conditions. However, serotype replacement by non-vaccine serotypes, the persistence of some vaccine serotypes, and divergence of serotypes between children and adults have limited the impact of pediatric PCV programs on adult populations. Designing complementary vaccines that leverage indirect protection from pediatric immunization and target the most prevalent adult serotypes may be a preferred strategy to maximize the public health impact of pneumococcal vaccination.
Keywords: Indirect protection; PCV; nasopharyngeal carriage; pneumococcal conjugate vaccine; pneumococcal disease; pneumonia.
Introduction: Pneumococcal vaccines protect against pneumococcal disease, caused by a bacterium called Streptococcus pneumoniae. There are two main types of pneumococcal disease: invasive (in which the disease enters normally bacteria-free sites, such as blood) and noninvasive (including pneumonia). Pneumococcal vaccination programs in children have lowered the occurrence of pneumococcal disease in vaccinated children (known as direct protection) and also in children and adults who have not been vaccinated (known as indirect protection).What does this review show: This review focuses on the indirect protection of adults provided by pneumococcal vaccination in children. The information presented shows that the number of pneumococcal cases in adults decreased after using pneumococcal vaccines in children because of indirect protection. Fewer adults were also found to carry the bacterium in their nose and throat. Factors affecting indirect protection against invasive pneumococcal disease are also discussed.Expert opinion: There are different types of S. pneumoniae called strains or serotypes. They differ based on the proteins and sugars found on the outer surface of the bacterium. Pneumococcal vaccines are designed to target a range of different serotypes. Pneumococcal vaccination in children has greatly decreased invasive and noninvasive pneumococcal disease caused by serotypes found in current vaccines in both older and younger adults, including those with other medical conditions. However, pneumococcal disease caused by serotypes not targeted by current vaccines is increasing. Developing vaccines that complement childhood vaccination can help address this persistent adult pneumococcal disease burden and improve public health benefits for both children and adults.