Invasive and Noninvasive Streptococcus pneumoniae Capsule and Surface Protein Diversity following the Use of a Conjugate Vaccine

The 13-valent pneumococcal conjugate vaccine (PCV13) was introduced in the United States in 2010 for the prevention of invasive pneumococcal disease (IPD) and otitis media. While many studies have reported its potential efficacy for IPD, not much is known about the epidemiology of noninvasive disease following its introduction. We characterized the capsular types and surface protein genes of noninvasive pediatric pneumococcal isolates collected between 2002 and 2010 (n = 1,058) at Children's of Alabama following the introduction of PCV7 and tested a subset of noninvasive and previously characterized IPD isolates for the presence of the pspA, pspC, and rrgC genes, which encode protection-eliciting proteins. PCV7 serotypes had dramatically decreased by 2010 (P < 0.0001), and only 50% of all noninvasive infections were caused by the PCV13 capsular serotypes. Serotype 19A accounted for 32% of the non-invasive isolates, followed by serotypes 35B (9%), 19F (7%), and 6C (6%). After 7 years of PCV7 usage, there were no changes in the frequencies of the pspA or pspC genes; 96% of the strains were positive for family 1 or 2 pspA genes, and 81% were also positive for pspC. Unexpectedly, more noninvasive than invasive strains were positive for rrgC (P < 0.0001), and the proportion of rrgC-positive strains in 2008 to 2010 was greater than that in 2002 to 2008 (IPD, P < 0.02; noninvasive, P < 0.001). Serotypes 19F, 19A, and 35B were more frequently rrgC positive (P < 0.005) than other serotypes. A vaccine containing antigens, such as PspA, PspC, and/or RrgC, can provide coverage against most non-PCV13-type pneumococci. Continued surveillance is critical for optimal future vaccine development.