Serotype | OPA GMTs at^{b}: | |||||||
---|---|---|---|---|---|---|---|---|

Prevaccination | Postvaccination | |||||||

50–64 yr (n = 142–159) | ≥65 yr (n = 146–161) | Comparison^{c} | 50–64 yr (n = 148–155) | ≥65 yr (n = 150–159) | Comparison^{c} | |||

Ratio | 95% CI | Ratio | 95% CI | |||||

1 | 6 | 7 | 0.8 | 0.64, 1.00 | 120 | 84 | 1.4 | 0.96, 2.10 |

3 | 7 | 11 | 0.6 | 0.48, 0.86 | 88 | 89 | 1.0 | 0.74, 1.33 |

4 | 30 | 53 | 0.6 | 0.32, 1.06 | 1,729 | 1,209 | 1.4 | 1.05, 1.95 |

5 | 7 | 10 | 0.7 | 0.51, 0.99 | 288 | 285 | 1.0 | 0.65, 1.58 |

6A | 57 | 110 | 0.5 | 0.30, 0.91 | 3,380 | 3,343 | 1.0 | 0.73, 1.39 |

6B | 235 | 388 | 0.6 | 0.33, 1.10 | 3,982 | 3,384 | 1.2 | 0.88, 1.58 |

7F | 66 | 125 | 0.5 | 0.29, 0.98 | 3,130 | 1,929 | 1.6 | 1.25, 2.11 |

9V | 264 | 173 | 1.5 | 0.81, 2.88 | 2,416 | 1,402 | 1.7 | 1.17, 2.54 |

14 | 291 | 361 | 0.8 | 0.50, 1.30 | 1,569 | 1,316 | 1.2 | 0.89, 1.60 |

18C | 70 | 155 | 0.4 | 0.24, 0.83 | 3,063 | 2,197 | 1.4 | 0.99, 1.96 |

19A | 52 | 105 | 0.5 | 0.32, 0.77 | 1,542 | 1,196 | 1.3 | 0.98, 1.70 |

19F | 26 | 53 | 0.5 | 0.29, 0.85 | 1104 | 1,188 | 0.9 | 0.63, 1.38 |

23F | 13 | 25 | 0.5 | 0.34, 0.82 | 879 | 930 | 0.9 | 0.60, 1.48 |

↵a OPA, opsonophagocytic activity; GMT, geometric mean titer.

↵b

*n*values are the numbers of subjects with a valid and determinate OPA titer to the given serotype. The GMTs were calculated using all subjects with available data for the specified blood draw.↵c The ratio of GMTs (50 to 64 years GMT/≥65 years GMT) was calculated by back transforming the mean difference between the age groups on the logarithmic scale. The 95% confidence intervals (CIs) for the ratios are back transformations of a CI based on the Student

*t*distribution for the mean difference of the logarithms of the measures (50 to 64 years data − ≥65 years data). The statistically significant differences are in bold type.