Persistent circulation of vaccine serotypes and serotype replacement after five years of UK infant immunisation with PCV13.
Kandasamy R., Voysey M., Collins S., Berbers G., Robinson H., Noel I., Hughes H., Ndimah S., Gould K., Fry N., Sheppard C., Ladhani S., Snape MD., Hinds J., Pollard AJ.
BACKGROUND: Following programmatic introduction of the 13-valent pneumococcal conjugate vaccine (PCV13), there is residual carriage and disease due to PCV13 covered serotypes. METHODS: 988 PCV13-immunised children aged 13-48 months were enrolled between February 2014 and August 2015 (late-PCV13), and had nasopharyngeal pneumococcal carriage compared with 567 PCV7-immunised children enrolled into a study between November 2010 and September 2011 (early-PCV13). Nasopharyngeal pneumococci were molecular-serotyped by microarray. Invasive pneumococcal disease (IPD) cases were identified through enhanced national surveillance. Blood collected from the late-PCV13 cohort was assessed for levels of serotype-specific serum IgG by multiplex immunoassay. RESULTS: Compared with PCV7-immunised children, carriage among PCV13-immunised children was significantly lower for serotypes 19A (OR=0.08, 95% CI 0.02-0.25), 6C (OR=0.11, 95% CI 0.03-0.32) and 7F (8 vs 0 cases).IPD incidence in children <5 years was significantly lower for serotypes 1 (IRR=0.03, 95% CI 0-0.19) and 7F (IRR=0.13, 95% CI 0.05-0.36) but not 19A (IRR=0.6, 95% CI 0.3-1.12) or serotype 3 (IRR=2.3, 95% CI 0.86-6.15) in the late-PCV13 period than in the early-PCV13 period. The most significant rises in IPD incidence were for serotypes 8, 12F, and 24F.Children from the late-PCV13 period, who had serum analysed, and were not carrying a PCV13 serotype, had high levels of antibody presumed to be due to natural exposure, to serotypes 3 (24/204, 11.76%) and 19A (14/204, 6.86%). CONCLUSIONS: PCV13 has reduced serotype 19A carriage among vaccinated children however, disease is not fully controlled. We also found, no impact of PCV13 on serotype 3 carriage or disease, and emergence of non-PCV13 serotype disease.