- Regev-Yochay, Gili;
- Hanage, William P;
- Trzcinski, Krzysztof;
- Rifas-Shiman, Sheryl L;
- Lee, Grace;
- Bessolo, Andrew;
- Huang, Susan S;
- Pelton, Stephen I;
- McAdam, Alexander J;
- Finkelstein, Jonathan A;
- Lipsitch, Marc;
- Malley, Richard
Pneumococcal type 1 pilus proteins have been proposed as potential vaccine candidates. Following conjugate pneumococcal vaccination, the prevalence of the pneumococcal type 1 pilus declined dramatically, a decline associated with the elimination of vaccine-type (VT) strains. Here we show that between 2004 and 2007, there has been a significant increase in pilus prevalence, now exceeding rates from the pre-conjugate vaccine era. This increase is primarily due to non-VT strains. These emerging piliated non-VT strains are mostly novel clones, with some exceptions. The rise in pilus type 1 frequency across multiple distinct genetic backgrounds suggests that the pilus may confer an intrinsic advantage.