Clinical and Epidemiological Evidence of the Red Queen Hypothesis in Pneumococcal Serotype Dynamics

Abstract

Background. The Red Queen hypothesis is an evolutionary theory that describes the reciprocal coevolution of competing species. We sought to study whether introduction of the 7- and 13-valent pneumococcal conjugate vaccines (PCV7 and PCV13, respectively) altered pneumococcal serotype dynamics among children with invasive pneumococcal disease (IPD) as predicted by the Red Queen hypothesis. Methods. This study examined pneumococcal isolates (n = 641) obtained from children <18 years of age hospitalized with IPD from 1997 to 2014 in Utah. A review of the literature also identified several additional studies conducted in the United States and Europe that were used to test the external generalizability of our Utah findings. Simpson's index was used to quantify pneumococcal serotype diversity. Results. In Utah, the introduction of PCV7 and PCV13 was associated with rapid increases in serotype diversity (P