The article discusses the evidence for serotype replacement in pneumococcal disease following the introduction of the protein-polysaccharide conjugate vaccine (PCV7). While PCV7 has significantly reduced pneumococcal disease in populations where it is widely used, there are concerns that non-vaccine serotypes (NVTs) could increase in prevalence and reduce the benefits of vaccination. The authors review the evidence for serotype replacement in carriage and disease, addressing potential biases in surveillance data and the invasiveness of different serotypes. They find that while complete serotype replacement has occurred in carriage, the increase in NVT disease has been less than the increase in NVT carriage, likely due to the lower invasiveness of NVTs. The article also discusses the potential impact of serotype replacement in future vaccination programs, particularly in developing countries, and emphasizes the need for ongoing surveillance to monitor the effectiveness of vaccines.The article discusses the evidence for serotype replacement in pneumococcal disease following the introduction of the protein-polysaccharide conjugate vaccine (PCV7). While PCV7 has significantly reduced pneumococcal disease in populations where it is widely used, there are concerns that non-vaccine serotypes (NVTs) could increase in prevalence and reduce the benefits of vaccination. The authors review the evidence for serotype replacement in carriage and disease, addressing potential biases in surveillance data and the invasiveness of different serotypes. They find that while complete serotype replacement has occurred in carriage, the increase in NVT disease has been less than the increase in NVT carriage, likely due to the lower invasiveness of NVTs. The article also discusses the potential impact of serotype replacement in future vaccination programs, particularly in developing countries, and emphasizes the need for ongoing surveillance to monitor the effectiveness of vaccines.