Impact of pneumococcal polysaccharide vaccine in people aged 65 years or older
In reply: We agree with Collignon that pneumococcal conjugate vaccines (PCVs) are superior to polysaccharide pneumococcal vaccines (PPVs), and that the herd immunity impact of the PCV on older people is impressive. However, we do not agree that our study shows that the PPV is ineffective in older people, or that its use has resulted in an increase in disease.
The increases in disease due to serotypes not contained in the 7-valent PCV in the ≥ 65-year age group suggest an underlying increase in adults, probably because of serotype replacement driven by the PCV. The fact that these increases were greater in 50–64-year-olds, in whom PPV use was negligible, suggests an attenuating effect from the PPV. The estimate of effectiveness of the PPV in our study was 61%.
Decisions on the PPV’s continued use in older people will depend on several factors. These include disease rates in older adults due to serotypes covered by the PPV but not the 13-valent PCV, and any likely additional impact of PCV use in adults over and above the herd immunity impacts from PCV use in children.